Merge station-services: sell and repair at a docked station, priced by one engine-free owner

Soul gate closed at verdict cut-station-services.s4 (head daa9a839). Merged under operator ruling aetheria-release:ruling:completed-cuts-merge.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Assets/Scenes/ARPG.unity

@@ -16674,7 +16674,6 @@ MonoBehaviour:
   m_Name: 
   m_EditorClassIdentifier: 
   Settings: {fileID: 11400000, guid: cd2344e2001a37544aab0960c164d4ff, type: 2}
-  Credits: 100000000
   TargetSpottedBlinkFrequency: 20
   TargetSpottedBlinkOffset: -0.25
   DeathPostTransitionTime: 1

Assets/Scripts/Gameplay/ActionGameManager.cs

@@ -111,7 +111,8 @@ public class ActionGameManager : MonoBehaviour
 
     public GameSettings Settings;
     //public string StarterShipTemplate = "Longinus";
-    public int Credits = 15000000;
+    // The run's credits: seeded from the scenario stage on a new game and from SavedGame on Continue, written by SaveRun.
+    [NonSerialized] public int Credits;
     public float TargetSpottedBlinkFrequency = 20;
     public float TargetSpottedBlinkOffset = -.25f;
     
@@ -252,7 +253,7 @@ public class ActionGameManager : MonoBehaviour
         if (CurrentGalaxy != null)
         {
             var (game, zones) = RunSave.Capture(CultCache, CurrentGalaxy, Zone, DockedEntity ?? CurrentEntity,
-                _actionBarSlots.Select(s => s.Save()).ToArray());
+                _actionBarSlots.Select(s => s.Save()).ToArray(), Credits);
             RunSave.Commit(CultCache, game, zones, ItemManager.Lots);
         }
     }
@@ -774,6 +775,7 @@ public class ActionGameManager : MonoBehaviour
             else
             {
                 var saved = CultCache.GetGlobal<SavedGame>();
+                Credits = saved.Credits;
                 foreach(var group in CurrentGalaxy.DiscoveredZones
                     .GroupBy(dz=>dz.Distance[CurrentGalaxy.Entrance]))
                     SectorMap.QueueZoneReveal(group);
@@ -829,6 +831,7 @@ public class ActionGameManager : MonoBehaviour
             MainMenu.Refuse($"{scenario.Name} could not start", string.Join("\n", failures));
             return;
         }
+        Credits = staged.Credits;
         SectorMap.QueueZoneReveal(CurrentGalaxy.Entrance.AdjacentZones.Prepend(CurrentGalaxy.Entrance));
         BindToEntity(staged.Player);
     }

Assets/Scripts/ServerShared/RunStart.cs

@@ -12,6 +12,7 @@ public static class RunStart
     public sealed class Staged
     {
         public Ship Player;
+        public int Credits;                       // the run's starting credits, as the scenario left them
         public List<Entity> Entities;             // what the scenario placed besides the player, in its order
     }
 
@@ -54,7 +55,7 @@ public static class RunStart
             player.SetIff(placed.Entity, hostile);
             arena.Admit(placed.Entity, placed.Piloted);
         }
-        return new Staged { Player = player, Entities = stage.Placed.Select(placed => placed.Entity).ToList() };
+        return new Staged { Player = player, Credits = stage.Credits, Entities = stage.Placed.Select(placed => placed.Entity).ToList() };
     }
 
     // A new run's item draws (each lot's quality, each generated fit) come from its galaxy's seed, not the process clock,

Assets/Scripts/ServerShared/SavedGame.cs

@@ -47,6 +47,9 @@ public class SavedGame
 
     [Key(12)]
     public FactionRelationship[] Relationships;
+
+    [Key(13)]
+    public int Credits;
 }
 
 // The run's lifecycle over the run store. Only Commit creates SavedGame, SavedZone and ProvenanceLedger records;
@@ -55,7 +58,7 @@ public static class RunSave
 {
     // The live run as plain documents. Writes nothing.
     public static (SavedGame Game, SavedZone[] Zones) Capture(CultCache cache, Galaxy galaxy, Zone currentZone,
-        Entity currentEntity, SavedActionBarBinding[] actionBar)
+        Entity currentEntity, SavedActionBarBinding[] actionBar, int credits)
     {
         var factions = galaxy.HomeZones.Keys.ToArray();
         var game = new SavedGame
@@ -75,7 +78,8 @@ public static class RunSave
             Entrance = Array.IndexOf(galaxy.Zones, galaxy.Entrance),
             Exit = Array.IndexOf(galaxy.Zones, galaxy.Exit),
             IsTutorial = galaxy.IsPrelude,
-            ActionBarBindings = actionBar
+            ActionBarBindings = actionBar,
+            Credits = credits
         };
 
         // A zone generated earlier but not loaded this session has no live Contents; its packed contents carry over.

Assets/Scripts/ServerShared/ScenarioStage.cs

@@ -24,6 +24,7 @@ public sealed class ScenarioStage
         Arena = arena;
         StartingHull = startingHull;
         TutorialGenerationSettings = tutorialGenerationSettings;
+        Credits = items.GameplaySettings.StartingCredits;
         // A fit names designs, not manufacturers, so what the galaxy offers decides which product builds each one.
         _available = new LoadoutGenerator(ref items.Random, items, arena.Galaxy, arena.GalaxyZone, null, 2).IsAvailable;
     }
@@ -33,6 +34,9 @@ public sealed class ScenarioStage
     public string StartingHull { get; }
     public TutorialGenerationSettings TutorialGenerationSettings { get; }
 
+    // What the run starts with: the gameplay settings' starting credits unless the scenario sets another amount.
+    public int Credits { get; set; }
+
     internal IReadOnlyList<string> Failures => _failures;
     internal bool PlayerPlaced { get; private set; }
     internal Ship PlayerShip { get; private set; }

Assets/Scripts/ServerShared/Settings.cs

@@ -161,6 +161,11 @@ public class GameplaySettings
     public EntitySettings DefaultEntitySettings;
     public RarityTier[] Tiers;
     public ExponentialLerp QualityPriceModifier;
+    // What a station pays for goods, as a fraction of their price, scaled further by the item's condition.
+    public float SellFraction = .5f;
+    // What a station charges to restore worn gear, as a fraction of the price of the wear.
+    public float RepairFraction = .25f;
+    public int StartingCredits = 15000000;
     public float DurabilityQualityExponent = 2;
     public float DurabilityQualityMin = 2;
     public float DurabilityQualityMax = .25f;

Assets/Scripts/ServerShared/StationServices.cs

@@ -0,0 +1,141 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+// What a station pays for goods and charges to mend gear. The one owner of the sell price, the repair cost, and the
+// two commits that move goods or restore durability against the run's credits; TradeMenu shows these numbers and
+// decides none of them. It holds no Unity type. Credits are the caller's: a refusal leaves them, the cargo and the
+// durabilities exactly as they were.
+public static class StationServices
+{
+    // What the station charges for the item, or for `quantity` units of a commodity (a crafted item is one unit). The
+    // number TradeMenu shows, checks against the run's credits and charges.
+    public static int BuyPrice(ItemManager items, ItemInstance item, int quantity = 1)
+    {
+        switch (item)
+        {
+            case CraftedItemInstance crafted:
+                return items.GetPrice(crafted);
+            case SimpleCommodity commodity:
+                return (int) Math.Min((long) items.GetData(commodity).Price * quantity, int.MaxValue);
+            default:
+                throw new ArgumentException($"{item?.GetType().Name ?? "null"} has no buy price.", nameof(item));
+        }
+    }
+
+    // What the station pays for the item: its price, scaled by SellFraction and by its condition. A commodity has no
+    // wear, so it sells at the fraction alone; a simple commodity's price is per unit.
+    public static int SellPrice(ItemManager items, ItemInstance item)
+    {
+        var fraction = (double) items.GameplaySettings.SellFraction;
+        switch (item)
+        {
+            case CraftedItemInstance crafted:
+                return SellValue(items.GetPrice(crafted), fraction, Condition(items, crafted));
+            case SimpleCommodity commodity:
+                return (int) Math.Floor((long) items.GetData(commodity).Price * commodity.Quantity * fraction);
+            default:
+                throw new ArgumentException($"{item?.GetType().Name ?? "null"} has no sell price.", nameof(item));
+        }
+    }
+
+    // What the station charges to restore the entity's hull armour, hull and every item it carries to design: each
+    // piece's share of its price in proportion to its wear, scaled by the repair fraction, rounded up. Armour has no
+    // price of its own, so the worn share of the hull's total armour is charged as that share of the hull's price.
+    public static int RepairCost(ItemManager items, Entity entity)
+    {
+        var fraction = RepairFraction(items);
+        long total = (long) Math.Ceiling(ArmourWear(entity) * items.GetPrice(entity.Hull) * fraction);
+        foreach (var gear in Gear(entity)) total += RepairShare(items, gear, fraction);
+        return (int) Math.Min(total, int.MaxValue);
+    }
+
+    // What the station charges for each unit of wear it mends: RepairFraction, but never less than SellFraction, so
+    // mending an item before selling it never pays more than the repair cost.
+    private static double RepairFraction(ItemManager items) =>
+        Math.Max(items.GameplaySettings.RepairFraction, items.GameplaySettings.SellFraction);
+
+    // The worn share of the entity's armour, 0 when it is whole or has none.
+    private static double ArmourWear(Entity entity)
+    {
+        double max = 0, worn = 0;
+        for (var x = 0; x < entity.MaxArmor.GetLength(0); x++)
+            for (var y = 0; y < entity.MaxArmor.GetLength(1); y++)
+            {
+                max += entity.MaxArmor[x, y];
+                worn += Math.Max(0, entity.MaxArmor[x, y] - entity.Armor[x, y]);
+            }
+        return max > 0 ? worn / max : 0;
+    }
+
+    // The purchase: the station charges BuyPrice, and `deliver` puts the goods where they go. Credits are checked
+    // and charged here, at the same boundary as TryRepair: a price equal to the credits held is affordable.
+    public static BuyResult TryBuy(ItemManager items, ItemInstance item, int quantity, ref int credits, Func<bool> deliver)
+    {
+        var price = BuyPrice(items, item, quantity);
+        if (price > credits) return BuyResult.ShortOfCredits;
+        if (!deliver()) return BuyResult.NoRoom;
+        credits -= price;
+        return BuyResult.Bought;
+    }
+
+    // The sale: the item leaves the bay for one of the station's cargo bays and the station pays SellPrice. False,
+    // with the item in its bay and the credits unchanged, when no station bay can take it.
+    public static bool TrySell(EquippedCargoBay from, Entity station, ItemInstance item, ref int credits)
+    {
+        var price = SellPrice(station.ItemManager, item);
+        var moved = item is SimpleCommodity commodity
+            ? station.CargoBays.Any(bay => from.TryTransferItem(bay, commodity, commodity.Quantity))
+            : station.CargoBays.Any(bay => from.TryTransferItem(bay, (CraftedItemInstance) item));
+        if (!moved) return false;
+        credits += price;
+        return true;
+    }
+
+    // The repair: armour and every durability go back to design and the station charges RepairCost. False, with
+    // nothing restored, when the credits fall short.
+    public static bool TryRepair(Entity entity, ref int credits)
+    {
+        var items = entity.ItemManager;
+        var cost = RepairCost(items, entity);
+        if (cost > credits) return false;
+        foreach (var gear in Gear(entity))
+            if (items.GetData(gear) is EquippableItemData design && design.Durability > 0)
+                gear.Durability = design.Durability;
+        Array.Copy(entity.MaxArmor, entity.Armor, entity.MaxArmor.Length);
+        credits -= cost;
+        return true;
+    }
+
+    // Equipment holds the hull itself, so the hull is in the sum once.
+    private static IEnumerable<EquippableItem> Gear(Entity entity) =>
+        entity.Equipment.Select(equipped => equipped.EquippableItem)
+            .Concat(entity.CargoBays.Select(bay => bay.EquippableItem))
+            .Concat(entity.DockingBays.Select(bay => bay.EquippableItem));
+
+    // Instance durability over the design's, for gear that wears; everything else is as good as new.
+    private static double Condition(ItemManager items, CraftedItemInstance item)
+    {
+        if (!(item is EquippableItem gear) || !(items.GetData(gear) is EquippableItemData design) || design.Durability <= 0)
+            return 1;
+        return Math.Max(0, Math.Min(1, gear.Durability / (double) design.Durability));
+    }
+
+    // The sell value of a price at a condition, rounded down. The one place the sell rounding lives: RepairShare
+    // prices the sell value a repair adds from the same function, so the two cannot round apart.
+    private static int SellValue(int price, double fraction, double condition) =>
+        (int) Math.Floor(price * fraction * condition);
+
+    // The share of the repair charge for one piece of gear: its wear at the repair fraction, rounded up, and never
+    // less than the sell value the repair adds, so mending before selling never nets credits.
+    private static long RepairShare(ItemManager items, EquippableItem gear, double fraction)
+    {
+        var price = items.GetPrice(gear);
+        var condition = Condition(items, gear);
+        var sellFraction = (double) items.GameplaySettings.SellFraction;
+        var added = SellValue(price, sellFraction, 1) - SellValue(price, sellFraction, condition);
+        return Math.Max(added, (long) Math.Ceiling((1 - condition) * price * fraction));
+    }
+}
+
+public enum BuyResult { Bought, ShortOfCredits, NoRoom }

Assets/Scripts/ServerShared/StationServices.cs.meta

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: efc90d4ec994710468cd5df6ed2c2739
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData:
+  assetBundleName:
+  assetBundleVariant:

Assets/Scripts/UI/Menu/TradeMenu.cs

@@ -25,6 +25,8 @@ public class TradeMenu : MonoBehaviour
     public TextMeshProUGUI CreditsLabel;
 
     private EquippedCargoBay _targetCargo;
+    // False lists the station's wares to buy; true lists the selected bay's goods to sell.
+    private bool _selling;
     private (ItemFilter filter, HardpointType type) _hardpointFilter;
     private (ItemFilter filter, SimpleCommodityCategory type) _commodityFilter;
     private (ItemFilter filter, CompoundCommodityCategory type) _compoundCommodityFilter;
@@ -36,6 +38,7 @@ public class TradeMenu : MonoBehaviour
     {
         if (GameManager.DockedEntity == null) return;
         _targetCargo = GameManager.DockingBay;
+        _selling = false;
         TargetCargoLabel.text = "Docking Bay";
         Properties.GameManager = GameManager;
         UpdateCreditsLabel();
@@ -185,13 +188,13 @@ public class TradeMenu : MonoBehaviour
 
     void Populate()
     {
-        var columns = new List<(string name, int size, Func<(ItemInstance item, ItemData data), Func<string>> output, Func<ItemData, IComparable> sortKey)>();
+        var columns = new List<(string name, int size, Func<(ItemInstance item, ItemData data), Func<string>> output, Func<(ItemInstance item, ItemData data), IComparable> sortKey)>();
         
         columns.Add(("Name", 3,
             x => () => x.item is CraftedItemInstance craftedItemInstance ? 
                 $"<color=#{ColorUtility.ToHtmlStringRGB(GameManager.ItemManager.GetTier(craftedItemInstance).tier.Color.ToColor())}>{x.data.Name}" : 
                 x.data.Name, 
-            data => data.Name));
+            x => x.data.Name));
         if(_hardpointFilter.filter==null)
             columns.Add(("Type", 2,
                 x => () =>
@@ -201,8 +204,9 @@ public class TradeMenu : MonoBehaviour
                     if(x.data is EquippableItemData e) return Enum.GetName(typeof(HardpointType), e.HardpointType);
                     return "None";
                 }, 
-                data => 
+                x =>
                 {
+                    var data = x.data;
                     if (data is SimpleCommodityData s) return (int) s.Category;
                     var offset = Enum.GetValues(typeof(SimpleCommodityCategory)).Length;
                     if(data is CompoundCommodityData c) return (int) c.Category + offset;
@@ -212,15 +216,15 @@ public class TradeMenu : MonoBehaviour
                 }));
         columns.Add(("Mass", 1,
             x => () => ActionGameManager.PlayerSettings.Format(x.data.Mass), 
-            data => data.Mass));
+            x => x.data.Mass));
         columns.Add(("Price", 1,
-            x => () => (x.item is CraftedItemInstance craftedItemInstance ? GameManager.ItemManager.GetPrice(craftedItemInstance) : x.data.Price).ToString("N0"),
-            data => data.Price));
+            x => () => ShownPrice(x.item).ToString("N0"),
+            x => ShownPrice(x.item)));
         columns.Add(("Size", 1,
             x => () => $"{x.data.Shape.Width}x{x.data.Shape.Height}", 
-            data => data.Shape.Width*data.Shape.Height));
+            x => x.data.Shape.Width*x.data.Shape.Height));
         
-        var items = Inventory.Cargo.Keys
+        var items = (_selling ? _targetCargo : Inventory).Cargo.Keys
             .Select<ItemInstance, (ItemInstance item, ItemData data)>(ii=>(ii, GameManager.ItemManager.GetData(ii)));
         
         if (MinimumSizeFilter.gameObject.activeSelf)
@@ -254,8 +258,9 @@ public class TradeMenu : MonoBehaviour
                     {
                         var behavior = ((EquippableItemData) x.data).Behaviors.FirstOrDefault(b => type.IsInstanceOfType(b));
                         return () => ActionGameManager.PlayerSettings.Format((float) field.GetValue(behavior));
-                    }, data =>
+                    }, x =>
                     {
+                        var data = x.data;
                         var behavior = ((EquippableItemData) data).Behaviors.FirstOrDefault(b => type.IsInstanceOfType(b));
                         return (float) field.GetValue(behavior);
                     }));
@@ -264,8 +269,9 @@ public class TradeMenu : MonoBehaviour
                     {
                         var behavior = ((EquippableItemData) x.data).Behaviors.FirstOrDefault(b => type.IsInstanceOfType(b));
                         return () => ((int) field.GetValue(behavior)).ToString();
-                    }, data =>
+                    }, x =>
                     {
+                        var data = x.data;
                         var behavior = ((EquippableItemData) data).Behaviors.FirstOrDefault(b => type.IsInstanceOfType(b));
                         return (int) field.GetValue(behavior);
                     }));
@@ -275,8 +281,9 @@ public class TradeMenu : MonoBehaviour
                     {
                         var behavior = ((EquippableItemData) x.data).Behaviors.FirstOrDefault(b => type.IsInstanceOfType(b));
                         return () => ActionGameManager.PlayerSettings.Format(((PerformanceStat) field.GetValue(behavior)).Max);
-                    }, data =>
+                    }, x =>
                     {
+                        var data = x.data;
                         var behavior = ((EquippableItemData) data).Behaviors.FirstOrDefault(b => type.IsInstanceOfType(b));
                         return ((PerformanceStat) field.GetValue(behavior)).Max;
                     }));
@@ -293,8 +300,9 @@ public class TradeMenu : MonoBehaviour
                     return (_targetCargo.ItemsOfType.ContainsKey(GameManager.ItemManager.ItemData.RefOf(x.data).Key) ? _targetCargo.ItemsOfType[GameManager.ItemManager.ItemData.RefOf(x.data).Key].Cast<SimpleCommodity>().Sum(s=>s.Quantity) : 0).ToString();
                 return (_targetCargo.ItemsOfType.ContainsKey(GameManager.ItemManager.ItemData.RefOf(x.data).Key) ? _targetCargo.ItemsOfType[GameManager.ItemManager.ItemData.RefOf(x.data).Key].Count : 0).ToString();
             }, 
-            data =>
+            x =>
             {
+                var data = x.data;
                 if (data is HullData)
                     return GameManager.DockedEntity.Children.Count(s => s.Hull.Data.Key.Equals(GameManager.ItemManager.ItemData.RefOf(data).Key) && s is Ship {IsPlayerShip: true});
                 if(data is SimpleCommodityData)
@@ -310,11 +318,12 @@ public class TradeMenu : MonoBehaviour
                 Columns = columns.Select(x => new SpreadsheetEntryColumn
                 {
                     Output = x.output(i),
-                    SortKey = x.sortKey(i.data)
+                    SortKey = x.sortKey(i)
                 }).ToArray(),
                 OnClick = () => Properties.Inspect(i.item),
                 OnDoubleClick = () =>
                 {
+                    if (_selling) return;
                     switch (i.item)
                     {
                         case CraftedItemInstance c:
@@ -329,7 +338,13 @@ public class TradeMenu : MonoBehaviour
                 },
                 OnRightClick = () =>
                 {
-                    if (i.item is SimpleCommodity s)
+                    if (_selling)
+                    {
+                        ContextMenu.Clear();
+                        ContextMenu.AddOption($"Sell ({StationServices.SellPrice(GameManager.ItemManager, i.item):N0})", () => Sell(i.item));
+                        ContextMenu.Show();
+                    }
+                    else if (i.item is SimpleCommodity s)
                     {
                         ContextMenu.Clear();
                         ContextMenu.AddOption("Buy Quantity",
@@ -340,7 +355,7 @@ public class TradeMenu : MonoBehaviour
                                 Dialog.Title.text = $"Buying {i.data.Name}";
                                 Dialog.AddField("Quantity", 
                                     () => quantity, 
-                                    q => quantity = min(min(q, GameManager.Credits / i.data.Price), s.Quantity));
+                                    q => quantity = min(min(q, GameManager.Credits / StationServices.BuyPrice(GameManager.ItemManager, s)), s.Quantity));
                                 Dialog.Show(() =>
                                 {
                                     Buy(s,quantity);
@@ -355,6 +370,11 @@ public class TradeMenu : MonoBehaviour
             }));
     }
     
+    // The price the list shows and sorts by: what the station pays for the player's goods, what it charges otherwise.
+    private int ShownPrice(ItemInstance item) => _selling
+        ? StationServices.SellPrice(GameManager.ItemManager, item)
+        : StationServices.BuyPrice(GameManager.ItemManager, item);
+
     private void UpdateCreditsLabel()
     {
         if (CreditsLabel != null)
@@ -363,43 +383,47 @@ public class TradeMenu : MonoBehaviour
         }
     }
 
+    private void Sell(ItemInstance item)
+    {
+        if (StationServices.TrySell(_targetCargo, GameManager.DockedEntity, item, ref GameManager.Credits))
+        {
+            UpdateCreditsLabel();
+            Populate();
+            return;
+        }
+        Dialog.Clear();
+        Dialog.Title.text = "Unable to sell: Station Cargo Full!";
+        Dialog.Show();
+        Dialog.MoveToCursor();
+    }
+
+    private void Repair()
+    {
+        if (StationServices.TryRepair(GameManager.CurrentEntity, ref GameManager.Credits))
+        {
+            UpdateCreditsLabel();
+            return;
+        }
+        Dialog.Clear();
+        Dialog.Title.text = "Unable to repair: Insufficient Credits!";
+        Dialog.Show();
+        Dialog.MoveToCursor();
+    }
+
     private void Buy(CraftedItemInstance item)
     {
         var data = GameManager.ItemManager.GetData(item);
-        var price = GameManager.ItemManager.GetPrice(item);
-        if (price < GameManager.Credits)
+        if (data is HullData hullData && hullData.HullType != HullType.Ship)
+            throw new ArgumentException("Attempted to buy non-ship hull from station, WTF are you doing?!");
+        Bought(StationServices.TryBuy(GameManager.ItemManager, item, 1, ref GameManager.Credits, () =>
         {
-            if (data is HullData hullData)
+            if (data is HullData)
             {
-                if (hullData.HullType != HullType.Ship) throw new ArgumentException("Attempted to buy non-ship hull from station, WTF are you doing?!");
-
                 GameManager.CommissionShip(item as EquippableItem);
-
-                GameManager.Credits -= data.Price;
-                UpdateCreditsLabel();
+                return true;
             }
-            else if (Inventory.TryTransferItem(_targetCargo, item))
-            {
-                GameManager.Credits -= price;
-                UpdateCreditsLabel();
-            }
-            else
-            {
-                Dialog.Clear();
-                Dialog.Title.text = "Unable to buy: Insufficient Cargo Space!";
-                Dialog.Show();
-                Dialog.MoveToCursor();
-                return;
-            }
-        }
-        else
-        {
-            Dialog.Clear();
-            Dialog.Title.text = "Unable to buy: Insufficient Credits!";
-            Dialog.Show();
-            Dialog.MoveToCursor();
-            return;
-        }
+            return Inventory.TryTransferItem(_targetCargo, item);
+        }));
     }
 
     private void Buy(SimpleCommodity simpleCommodity, int quantity)
@@ -411,36 +435,29 @@ public class TradeMenu : MonoBehaviour
         for (int i = 0; i < lots; i++)
         {
             int q = min(remaining, data.MaxStack);
-            if (q * data.Price < GameManager.Credits)
-            {
-                if (Inventory.TryTransferItem(_targetCargo, simpleCommodity, quantity))
-                {
-                    GameManager.Credits -= q * data.Price;
-                    UpdateCreditsLabel();
-                    remaining -= q;
-                }
-                else
-                {
-                    Dialog.Clear();
-                    Dialog.Title.text = "Unable to buy: Insufficient Cargo Space!";
-                    Dialog.Show();
-                    Dialog.MoveToCursor();
-                    return;
-                }
-            }
-            else
-            {
-                Dialog.Clear();
-                Dialog.Title.text = "Unable to buy: Insufficient Credits!";
-                Dialog.Show();
-                Dialog.MoveToCursor();
-                return;
-            }
-
-            
+            if (!Bought(StationServices.TryBuy(GameManager.ItemManager, simpleCommodity, q, ref GameManager.Credits,
+                    () => Inventory.TryTransferItem(_targetCargo, simpleCommodity, quantity)))) return;
+            remaining -= q;
         }
     }
 
+    // Refreshes the credits after a purchase, or tells the player why the station refused it.
+    private bool Bought(BuyResult result)
+    {
+        if (result == BuyResult.Bought)
+        {
+            UpdateCreditsLabel();
+            return true;
+        }
+        Dialog.Clear();
+        Dialog.Title.text = result == BuyResult.NoRoom
+            ? "Unable to buy: Insufficient Cargo Space!"
+            : "Unable to buy: Insufficient Credits!";
+        Dialog.Show();
+        Dialog.MoveToCursor();
+        return false;
+    }
+
     void Start()
     {
         FoldoutButton.onClick.AddListener(() =>
@@ -468,6 +485,13 @@ public class TradeMenu : MonoBehaviour
                     }
                 }
             }
+            ContextMenu.AddOption(_selling ? "Buy Goods" : "Sell Goods", () =>
+            {
+                _selling = !_selling;
+                Populate();
+            });
+            var repairCost = StationServices.RepairCost(GameManager.ItemManager, GameManager.CurrentEntity);
+            if (repairCost > 0) ContextMenu.AddOption($"Repair ({repairCost:N0})", Repair);
             ContextMenu.Show();
         });
     }

tests/Aetheria.Shared.Tests/RunSaveTests.cs

@@ -91,7 +91,7 @@ public sealed class RunSaveTests : IDisposable
             var galaxy = new Galaxy(cache, cache.GetGlobal<SavedGame>(), _ => { });
             var itemManager = new ItemManager(cache, new ProvenanceLedger(), TestSettings(), _ => { });
             galaxy.Zones[0].Contents = new Zone(itemManager, new PlanetSettings(), new ZonePack(), galaxy.Zones[0], galaxy);
-            var (game, zones) = RunSave.Capture(cache, galaxy, galaxy.Zones[0].Contents, null, new SavedActionBarBinding[0]);
+            var (game, zones) = RunSave.Capture(cache, galaxy, galaxy.Zones[0].Contents, null, new SavedActionBarBinding[0], 0);
             RunSave.Commit(cache, game, zones, RunSave.Lots(cache));
         }
 
@@ -104,6 +104,26 @@ public sealed class RunSaveTests : IDisposable
         }
     }
 
+    // The run's credits ride the save: what Capture is given is what a later Continue reads from the run store.
+    [Fact]
+    public void CreditsSurviveContinue()
+    {
+        using (var cache = Open())
+            RunSave.Commit(cache, Game(cache), Zones(2, StageZoneContents(cache), 0), new ProvenanceLedger());
+
+        using (var cache = Open())
+        {
+            var galaxy = new Galaxy(cache, cache.GetGlobal<SavedGame>(), _ => { });
+            var itemManager = new ItemManager(cache, new ProvenanceLedger(), TestSettings(), _ => { });
+            galaxy.Zones[0].Contents = new Zone(itemManager, new PlanetSettings(), new ZonePack(), galaxy.Zones[0], galaxy);
+            var (game, zones) = RunSave.Capture(cache, galaxy, galaxy.Zones[0].Contents, null, new SavedActionBarBinding[0], 4242);
+            RunSave.Commit(cache, game, zones, RunSave.Lots(cache));
+        }
+
+        using (var cache = Open())
+            Assert.Equal(4242, cache.GetGlobal<SavedGame>().Credits);
+    }
+
     [Fact]
     public void ClearRemovesEveryRunRecord()
     {

tests/Aetheria.Shared.Tests/ScenarioTests.cs

@@ -108,6 +108,21 @@ public sealed partial class RunStartTests
         }
     }
 
+    // A run starts with the gameplay settings' starting credits unless its scenario sets another amount.
+    [Fact]
+    public void StagedCreditsAreTheSettingsUnlessTheScenarioSets()
+    {
+        var plain = Stage(Arena(true), new Scripted(true, stage => stage.Player(stage.Bare("Djinni"), float2(0, 0))));
+        Assert.Equal(_items.GameplaySettings.StartingCredits, plain.Credits);
+
+        var poor = Stage(Arena(true), new Scripted(true, stage =>
+        {
+            stage.Credits = 1234;
+            stage.Player(stage.Bare("Djinni"), float2(0, 0));
+        }));
+        Assert.Equal(1234, poor.Credits);
+    }
+
     // The two game modes are what New Game did: the tutorial a prelude galaxy and a starting-hull ship of the
     // protagonist faction at the entrance's origin; the main galaxy a main galaxy and a starting-hull ship there. Both
     // arenas keep their generated ships.
@@ -533,10 +548,10 @@ public sealed partial class RunStartTests
     public void SaveReadsPrelude()
     {
         var arena = Arena(true);
-        var (prelude, _) = RunSave.Capture(_cache, _galaxy, arena, null, new SavedActionBarBinding[0]);
+        var (prelude, _) = RunSave.Capture(_cache, _galaxy, arena, null, new SavedActionBarBinding[0], 0);
         Assert.True(prelude.IsTutorial);
 
-        var (main, _) = RunSave.Capture(_cache, MainSectorGalaxy(), arena, null, new SavedActionBarBinding[0]);
+        var (main, _) = RunSave.Capture(_cache, MainSectorGalaxy(), arena, null, new SavedActionBarBinding[0], 0);
         Assert.False(main.IsTutorial);
     }
 

tests/Aetheria.Shared.Tests/StationServicesTests.cs

@@ -0,0 +1,468 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using CultMath;
+using GameCult.Caching;
+using Xunit;
+
+// What a station pays and charges, and the commits that move goods and credits. The price rules are pinned against the
+// authored gameplay settings, so the defaults a Settings.asset without the new fields keeps are the ones tested.
+public sealed class StationServicesTests : IDisposable
+{
+    private readonly string _root = Path.Combine(Path.GetTempPath(), "aetheria-stationservices-" + Guid.NewGuid().ToString("N"));
+    private readonly CultCache _cache;
+    private readonly ItemManager _items;
+    private readonly Zone _zone;
+
+    public StationServicesTests()
+    {
+        Directory.CreateDirectory(_root);
+        _cache = AetheriaStores.Open(Path.Combine(_root, "Aetheria.cc"), catalogWritable: true);
+        _cache.Upsert(new TestCatalogGlobal { Name = "Temperament" });
+        var shape = new Shape(5, 5);
+        foreach (var cell in shape.AllCoordinates) shape[cell] = true;
+        var hardpoint = new HardpointData { Type = HardpointType.Sensors, Position = new int2(0, 0), Shape = new Shape() };
+        _cache.Upsert(new HullData { Name = "Skiff", HullType = HullType.Ship, Shape = shape, Price = 1000, Durability = 10, Armor = 10, Hardpoints = { hardpoint } });
+        _cache.Upsert(new HullData { Name = "Hub", HullType = HullType.Station, Shape = shape, Price = 5000, Durability = 10 });
+        _cache.Upsert(new HullData { Name = "Bare Hub", HullType = HullType.Station, Shape = shape, Price = 5000, Durability = 10 });
+        _cache.Upsert(new GearData { Name = "Gun", Hardpoint = HardpointType.Sensors, Shape = new Shape(), Price = 400, Durability = 8 });
+        _cache.Upsert(new GearData { Name = "Sweep", Hardpoint = HardpointType.Sensors, Shape = new Shape(), Price = 1, Durability = 20 });
+        _cache.Upsert(new GearData { Name = "Lamp", Hardpoint = HardpointType.Sensors, Shape = new Shape(), Price = 90, Durability = 0 });
+        var bay = new Shape(4, 4);
+        foreach (var cell in bay.AllCoordinates) bay[cell] = true;
+        _cache.Upsert(new CargoBayData { Name = "Crate", Shape = new Shape(), InteriorShape = bay, Price = 20, Durability = 4 });
+        _cache.Upsert(new DockingBayData { Name = "Berth", Shape = new Shape(), InteriorShape = bay, MaxSize = new int2(2, 2), Price = 60, Durability = 6 });
+        _cache.Upsert(new SimpleCommodityData { Name = "Ore", Shape = new Shape(), Price = 7, MaxStack = 100 });
+        _cache.FlushAsync().Wait();
+
+        var settings = AuthoredSettings.Load(RestoredHullsTests.FindRepoRoot()).Read<GameplaySettings>("GameplaySettings");
+        _items = new ItemManager(_cache, new ProvenanceLedger(), settings, _ => { });
+        _zone = new Zone(_items, new PlanetSettings(), new ZonePack(), new GalaxyZone { Name = "Test Zone", Owner = null }, null);
+    }
+
+    public void Dispose()
+    {
+        _cache.Dispose();
+        Directory.Delete(_root, true);
+    }
+
+    private EquippableItem Mint(string design, float? durability = null)
+    {
+        var data = _cache.GetByName<EquippableItemData>(design);
+        return new EquippableItem
+        {
+            Data = _cache.RefOf<ItemData>(data),
+            Durability = durability ?? data.Durability,
+            Lot = _items.Lots.Add(new Lot { Design = _cache.RefOf<ItemData>(data), Origin = new Attributed(), Quality = .5f, Roles = new List<RoleFill>() })
+        };
+    }
+
+    private SimpleCommodity Ore(int quantity) => new SimpleCommodity { Data = _cache.RefOf<ItemData>(_cache.GetByName<SimpleCommodityData>("Ore")), Quantity = quantity };
+
+    // A ship with a cargo bay.
+    private Ship Ship(float? hullDurability = null)
+    {
+        var ship = new Ship(_items, _zone, Mint("Skiff", hullDurability), new EntitySettings());
+        Assert.True(ship.TryEquip(Mint("Crate"), new int2(1, 1)));
+        return ship;
+    }
+
+    // A station whose one cargo bay can take the goods, or one with no cargo bay at all.
+    private OrbitalEntity Station(bool withBay = true)
+    {
+        var station = new OrbitalEntity(_items, _zone, Mint(withBay ? "Hub" : "Bare Hub"), default, new EntitySettings());
+        if (withBay) Assert.True(station.TryEquip(Mint("Crate"), new int2(1, 1)));
+        return station;
+    }
+
+    [Fact]
+    public void SettingsDefaultsAreHalfAndAQuarter()
+    {
+        Assert.Equal(.5f, _items.GameplaySettings.SellFraction);
+        Assert.Equal(.25f, _items.GameplaySettings.RepairFraction);
+        Assert.Equal(15000000, _items.GameplaySettings.StartingCredits);
+    }
+
+    [Fact]
+    public void BuyPrice_is_the_price_and_the_sale_never_beats_it()
+    {
+        Assert.Equal(_items.GetPrice(Mint("Gun")), StationServices.BuyPrice(_items, Mint("Gun")));
+        // A worn gun costs what a new one does to buy, and pays less to sell.
+        Assert.Equal(StationServices.BuyPrice(_items, Mint("Gun")), StationServices.BuyPrice(_items, Mint("Gun", 4)));
+        // A commodity is priced per unit, times the units asked for.
+        Assert.Equal(7, StationServices.BuyPrice(_items, Ore(10)));
+        Assert.Equal(70, StationServices.BuyPrice(_items, Ore(1), 10));
+        Assert.Equal(int.MaxValue, StationServices.BuyPrice(_items, Ore(1), int.MaxValue));
+        Assert.True(StationServices.SellPrice(_items, Mint("Gun")) < StationServices.BuyPrice(_items, Mint("Gun")));
+        Assert.Throws<ArgumentException>(() => StationServices.BuyPrice(_items, null));
+    }
+
+    [Fact]
+    public void SellPrice_scales_with_condition()
+    {
+        var price = _items.GetPrice(Mint("Gun"));
+        Assert.True(price > 100, "the fixture's gun must have a price large enough to show a half");
+        Assert.Equal((int) Math.Floor(price * .5), StationServices.SellPrice(_items, Mint("Gun")));
+        Assert.Equal((int) Math.Floor(price * .25), StationServices.SellPrice(_items, Mint("Gun", 4)));
+        Assert.Equal(0, StationServices.SellPrice(_items, Mint("Gun", 0)));
+
+        // A design with no durability does not wear, so it sells as new however its instance reads.
+        Assert.Equal((int) Math.Floor(_items.GetPrice(Mint("Lamp")) * .5), StationServices.SellPrice(_items, Mint("Lamp", 0)));
+        // Past design durability is no better than new.
+        Assert.Equal(StationServices.SellPrice(_items, Mint("Gun")), StationServices.SellPrice(_items, Mint("Gun", 80)));
+        // A commodity has no wear: its price per unit times the quantity, at the fraction, rounded down.
+        Assert.Equal(35, StationServices.SellPrice(_items, Ore(10)));
+        Assert.Equal(3, StationServices.SellPrice(_items, Ore(1)));
+        // A stack large enough that a scaled price shows: 7 * 100 * .5 is exactly 350, and a 2% larger fraction pays 357.
+        Assert.Equal(350, StationServices.SellPrice(_items, Ore(100)));
+    }
+
+    [Fact]
+    public void TrySell_moves_and_pays_or_refuses()
+    {
+        var ship = Ship();
+        var from = ship.CargoBays.Single();
+        var gun = Mint("Gun", 4);
+        var ore = Ore(10);
+        Assert.True(from.TryStore(gun));
+        Assert.True(from.TryStore(ore));
+        var station = Station();
+        var credits = 1000;
+
+        Assert.True(StationServices.TrySell(from, station, gun, ref credits));
+        Assert.Equal(1000 + StationServices.SellPrice(_items, Mint("Gun", 4)), credits);
+        Assert.DoesNotContain(gun, from.Cargo.Keys);
+        Assert.Contains(gun, station.CargoBays.Single().Cargo.Keys);
+
+        credits = 1000;
+        Assert.True(StationServices.TrySell(from, station, ore, ref credits));
+        Assert.Equal(1035, credits);
+        Assert.Empty(from.Cargo.Keys.OfType<SimpleCommodity>());
+        Assert.Equal(10, station.CargoBays.Single().Cargo.Keys.OfType<SimpleCommodity>().Sum(c => c.Quantity));
+
+        // A station with nowhere to put it takes nothing and pays nothing.
+        var other = Mint("Gun");
+        Assert.True(from.TryStore(other));
+        var packed = from.Cargo.Count;
+        credits = 1000;
+        Assert.False(StationServices.TrySell(from, Station(withBay: false), other, ref credits));
+        Assert.Equal(1000, credits);
+        Assert.Equal(packed, from.Cargo.Count);
+        Assert.Contains(other, from.Cargo.Keys);
+    }
+
+    // A station's first bay being full is no reason to refuse: the goods go to whichever bay takes them.
+    [Fact]
+    public void TrySell_uses_any_station_bay_that_takes_the_goods()
+    {
+        var ship = Ship();
+        var from = ship.CargoBays.Single();
+        var gun = Mint("Gun");
+        var ore = Ore(10);
+        Assert.True(from.TryStore(gun));
+        Assert.True(from.TryStore(ore));
+        var station = Station();
+        Assert.True(station.TryEquip(Mint("Crate"), new int2(2, 2)));
+        var full = station.CargoBays[0];
+        var open = station.CargoBays[1];
+        while (full.TryStore(Mint("Gun"))) { }
+
+        var credits = 0;
+        Assert.True(StationServices.TrySell(from, station, gun, ref credits));
+        Assert.True(StationServices.TrySell(from, station, ore, ref credits));
+        Assert.Contains(gun, open.Cargo.Keys);
+        Assert.Contains(ore, open.Cargo.Keys);
+    }
+
+    [Fact]
+    public void Repair_restores_and_charges()
+    {
+        var whole = Ship();
+        Assert.True(whole.TryEquip(Mint("Gun")));
+        Assert.Equal(0, StationServices.RepairCost(_items, whole));
+        var credits = 50;
+        Assert.True(StationServices.TryRepair(whole, ref credits));
+        Assert.Equal(50, credits);
+
+        var ship = Ship(hullDurability: 5);
+        Assert.True(ship.TryEquip(Mint("Gun", 2)));
+        var cost = StationServices.RepairCost(_items, ship);
+        var hull = (int) Math.Ceiling(.5 * _items.GetPrice(ship.Hull) * .5);
+        var gun = (int) Math.Ceiling(.75 * _items.GetPrice(Mint("Gun")) * .5);
+        Assert.Equal(hull + gun, cost);
+
+        var shortOfCost = cost - 1;
+        Assert.False(StationServices.TryRepair(ship, ref shortOfCost));
+        Assert.Equal(cost - 1, shortOfCost);
+        Assert.Equal(5, ship.Hull.Durability);
+        Assert.Equal(2, ship.Equipment.Single(e => e.EquippableItem != ship.Hull).EquippableItem.Durability);
+
+        var exact = cost;
+        Assert.True(StationServices.TryRepair(ship, ref exact));
+        Assert.Equal(0, exact);
+        Assert.Equal(10, ship.Hull.Durability);
+        Assert.Equal(8, ship.Equipment.Single(e => e.EquippableItem != ship.Hull).EquippableItem.Durability);
+        Assert.Equal(0, StationServices.RepairCost(_items, ship));
+    }
+
+    [Fact]
+    public void Repair_counts_docking_bays_as_gear()
+    {
+        var ship = Ship();
+        Assert.True(ship.TryEquip(Mint("Berth"), new int2(2, 2)));
+        var berth = ship.DockingBays.Single().EquippableItem;
+        berth.Durability = 3;
+        Assert.True(StationServices.RepairCost(_items, ship) > 0, "a worn docking bay costs to mend");
+        var credits = 1000000;
+        Assert.True(StationServices.TryRepair(ship, ref credits));
+        Assert.Equal(6, berth.Durability);
+    }
+
+    [Fact]
+    public void Repair_counts_cargo_bays_as_gear()
+    {
+        var ship = Ship();
+        ship.CargoBays.Single().EquippableItem.Durability = 1;
+        Assert.True(StationServices.RepairCost(_items, ship) > 0, "a worn cargo bay costs to mend");
+        var credits = 1000000;
+        Assert.True(StationServices.TryRepair(ship, ref credits));
+        Assert.Equal(4, ship.CargoBays.Single().EquippableItem.Durability);
+    }
+
+    [Fact]
+    public void Repair_restores_armour_at_a_price()
+    {
+        var ship = Ship();
+        Assert.Equal(0, StationServices.RepairCost(_items, ship));
+        ship.Armor[2, 2] = 0;
+        var cells = ship.MaxArmor.Length;
+        var share = 10.0 / (10.0 * cells);
+        var cost = StationServices.RepairCost(_items, ship);
+        Assert.Equal((int) Math.Ceiling(share * _items.GetPrice(ship.Hull) * .5), cost);
+        Assert.True(cost > 0, "armour-only wear offers a repair");
+
+        var short1 = cost - 1;
+        Assert.False(StationServices.TryRepair(ship, ref short1));
+        Assert.Equal(0, ship.Armor[2, 2]);
+
+        var exact = cost;
+        Assert.True(StationServices.TryRepair(ship, ref exact));
+        Assert.Equal(0, exact);
+        Assert.Equal(10, ship.Armor[2, 2]);
+        Assert.Equal(0, StationServices.RepairCost(_items, ship));
+    }
+
+    [Theory]
+    [InlineData(0.1f)]
+    [InlineData(0.25f)]
+    [InlineData(0.5f)]
+    [InlineData(0.9f)]
+    public void Repairing_then_selling_never_nets_credits(float repairFraction)
+    {
+        _items.GameplaySettings.RepairFraction = repairFraction;
+        for (var durability = 0; durability < 8; durability++)
+        {
+            var ship = Ship();
+            var gun = Mint("Gun", durability);
+            Assert.True(ship.TryEquip(gun));
+            var sellWorn = StationServices.SellPrice(_items, gun);
+            var cost = StationServices.RepairCost(_items, ship);
+            var credits = cost;
+            Assert.True(StationServices.TryRepair(ship, ref credits));
+            Assert.Equal(0, credits);
+            var sellFixed = StationServices.SellPrice(_items, gun);
+            Assert.True(sellFixed - cost <= sellWorn, $"durability {durability}: repair {cost} adds {sellFixed - sellWorn}");
+        }
+    }
+
+    // Mending an item and then selling it never nets even one credit over selling it worn, whatever the price, the
+    // wear and the fractions. Prices 1..3000 (the sell and repair roundings disagree for some of them in double
+    // arithmetic) at every durability of a design of 20, at the shipped fractions and two other pairs.
+    [Theory]
+    [InlineData(.5f, .25f)]
+    [InlineData(.3f, .1f)]
+    [InlineData(.7f, .2f)]
+    public void Repairing_then_selling_never_nets_a_credit_at_any_price_and_wear(float sell, float repair)
+    {
+        _items.GameplaySettings.SellFraction = sell;
+        _items.GameplaySettings.RepairFraction = repair;
+        var ship = Ship();
+        var design = _cache.GetByName<GearData>("Sweep");
+        var gear = Mint("Sweep");
+        Assert.True(ship.TryEquip(gear));
+        for (var price = 1; price <= 3000; price++)
+        {
+            design.Price = price;
+            for (var durability = 0; durability < 20; durability++)
+            {
+                gear.Durability = durability;
+                var sellWorn = StationServices.SellPrice(_items, gear);
+                var cost = StationServices.RepairCost(_items, ship);
+                var credits = cost;
+                Assert.True(StationServices.TryRepair(ship, ref credits));
+                var sellFixed = StationServices.SellPrice(_items, gear);
+                Assert.True(sellFixed - cost <= sellWorn,
+                    $"price {_items.GetPrice(gear)} durability {durability} of 20 at {sell}/{repair}: sell worn {sellWorn}, repair {cost}, sell fixed {sellFixed}");
+            }
+        }
+    }
+
+    // The case that nets a credit in plain double arithmetic: price 360 at durability 7 of 20 sells worn for 62 but
+    // 180 whole, and a repair rounded up from 65 percent of 180 is 117.
+    [Fact]
+    public void Repairing_a_360_item_at_durability_7_of_20_costs_at_least_what_it_adds()
+    {
+        var design = _cache.GetByName<GearData>("Sweep");
+        var gear = Mint("Sweep");
+        var ship = Ship();
+        Assert.True(ship.TryEquip(gear));
+        design.Price = Enumerable.Range(1, 3000).First(p => { design.Price = p; return _items.GetPrice(gear) == 360; });
+        Assert.Equal(360, _items.GetPrice(gear));
+        gear.Durability = 7;
+        Assert.Equal(62, StationServices.SellPrice(_items, gear));
+        var cost = StationServices.RepairCost(_items, ship);
+        Assert.True(cost >= 180 - 62, $"repair costs {cost}, the repair adds 118");
+        var credits = cost;
+        Assert.True(StationServices.TryRepair(ship, ref credits));
+        Assert.Equal(180, StationServices.SellPrice(_items, gear));
+    }
+
+    // A ship whose armour cells hold different values, wear spread over several cells including the last. Returns the
+    // total armour and the worn amount.
+    private static (double max, double worn) Wound(Ship ship, Func<int, int, float> armourLeft)
+    {
+        double max = 0, worn = 0;
+        for (var x = 0; x < ship.MaxArmor.GetLength(0); x++)
+            for (var y = 0; y < ship.MaxArmor.GetLength(1); y++)
+            {
+                ship.MaxArmor[x, y] = 4 + (x + 2 * y) % 5;
+                ship.Armor[x, y] = Math.Min(ship.MaxArmor[x, y], armourLeft(x, y));
+                max += ship.MaxArmor[x, y];
+                worn += ship.MaxArmor[x, y] - ship.Armor[x, y];
+            }
+        return (max, worn);
+    }
+
+    // Hull prices odd and even, so an armour price off by one in either direction moves the rounded cost.
+    [Theory]
+    [InlineData(0)]
+    [InlineData(1)]
+    [InlineData(2)]
+    [InlineData(3)]
+    [InlineData(4)]
+    public void Armour_repair_prices_the_worn_share_of_the_hull_and_restores_every_cell(int pattern)
+    {
+        var skiff = _cache.GetByName<HullData>("Skiff");
+        foreach (var hullPrice in new[] { 1000, 1001, 1337, 777, 4 })
+        {
+            skiff.Price = hullPrice;
+            var ship = Ship();
+            // 0: every cell stripped. 1: a few cells stripped, one of them the last. 2: every cell a little worn.
+            // 3: every cell worn by a fraction of a cell. 4: one cell worn by a thousandth, the rest whole.
+            var (max, worn) = Wound(ship, (x, y) => pattern switch
+            {
+                0 => 0,
+                1 => x + y >= 7 || (x == 0 && y == 0) || (x == 2 && y == 3) ? 0 : 99,
+                2 => 3,
+                3 => (x + y) % 3 == 0 ? 3.999f : (x + y) % 3 == 1 ? 3.5f : 3.25f,
+                _ => x == 2 && y == 2 ? 4.999f : 99
+            });
+            Assert.True(worn > 0 && worn <= max);
+            var price = _items.GetPrice(ship.Hull);
+            var expected = (int) Math.Ceiling(worn / max * price * .5);
+            var cost = StationServices.RepairCost(_items, ship);
+            Assert.Equal(expected, cost);
+            if (pattern == 0) Assert.Equal((int) Math.Ceiling(price * .5), cost);
+
+            var credits = cost;
+            Assert.True(StationServices.TryRepair(ship, ref credits));
+            Assert.Equal(0, credits);
+            for (var x = 0; x < ship.MaxArmor.GetLength(0); x++)
+                for (var y = 0; y < ship.MaxArmor.GetLength(1); y++)
+                    Assert.Equal(ship.MaxArmor[x, y], ship.Armor[x, y]);
+            Assert.Equal(0, StationServices.RepairCost(_items, ship));
+        }
+    }
+
+    // Gear alone is charged its wear at the repair fraction, rounded up, never below the sell value mending adds:
+    // odd and even prices at several wears, so a price off by one shows in the rounding.
+    [Fact]
+    public void Gear_repair_is_priced_from_the_gear_price_at_every_wear()
+    {
+        var ship = Ship();
+        var design = _cache.GetByName<GearData>("Sweep");
+        var gear = Mint("Sweep");
+        Assert.True(ship.TryEquip(gear));
+        foreach (var dataPrice in new[] { 3, 11, 37, 101, 250, 777, 1001 })
+        {
+            design.Price = dataPrice;
+            var price = _items.GetPrice(gear);
+            foreach (var durability in new[] { 0, 1, 5, 10, 19 })
+            {
+                gear.Durability = durability;
+                var wear = 1 - durability / 20.0;
+                var added = (int) Math.Floor(price * .5) - (int) Math.Floor(price * .5 * durability / 20.0);
+                var expected = Math.Max(added, (int) Math.Ceiling(wear * price * .5));
+                Assert.Equal(expected, StationServices.RepairCost(_items, ship));
+            }
+        }
+    }
+
+    // A repair fraction above the sell fraction prices wear at the repair fraction, and the sell value a repair adds
+    // stays at the sell fraction: the cost is the larger of the two, exactly, at every price and wear.
+    [Theory]
+    [InlineData(.3f, .6f)]
+    [InlineData(.5f, .9f)]
+    [InlineData(.1f, .75f)]
+    public void Gear_repair_above_the_sell_fraction_is_priced_at_the_repair_fraction(float sell, float repair)
+    {
+        _items.GameplaySettings.SellFraction = sell;
+        _items.GameplaySettings.RepairFraction = repair;
+        var ship = Ship();
+        var design = _cache.GetByName<GearData>("Sweep");
+        var gear = Mint("Sweep");
+        Assert.True(ship.TryEquip(gear));
+        double sellFraction = sell, repairFraction = repair;
+        for (var dataPrice = 1; dataPrice <= 400; dataPrice++)
+        {
+            design.Price = dataPrice;
+            var price = _items.GetPrice(gear);
+            for (var durability = 0; durability < 20; durability++)
+            {
+                gear.Durability = durability;
+                var condition = durability / 20.0;
+                var added = (int) Math.Floor(price * sellFraction) - (int) Math.Floor(price * sellFraction * condition);
+                var expected = Math.Max(added, (int) Math.Ceiling((1 - condition) * price * repairFraction));
+                Assert.True(expected == StationServices.RepairCost(_items, ship),
+                    $"price {price} durability {durability} of 20 at {sell}/{repair}: expected {expected}");
+            }
+        }
+    }
+
+    [Fact]
+    public void Buy_is_affordable_at_exactly_the_credits_held()
+    {
+        var gun = Mint("Gun");
+        var price = StationServices.BuyPrice(_items, gun);
+        var delivered = 0;
+        var credits = price - 1;
+        Assert.Equal(BuyResult.ShortOfCredits, StationServices.TryBuy(_items, gun, 1, ref credits, () => { delivered++; return true; }));
+        Assert.Equal(price - 1, credits);
+        Assert.Equal(0, delivered);
+
+        credits = price;
+        Assert.Equal(BuyResult.Bought, StationServices.TryBuy(_items, gun, 1, ref credits, () => { delivered++; return true; }));
+        Assert.Equal(0, credits);
+        Assert.Equal(1, delivered);
+
+        credits = price + 5;
+        Assert.Equal(BuyResult.NoRoom, StationServices.TryBuy(_items, gun, 1, ref credits, () => false));
+        Assert.Equal(price + 5, credits);
+
+        var ore = Ore(10);
+        credits = 70;
+        Assert.Equal(BuyResult.Bought, StationServices.TryBuy(_items, ore, 10, ref credits, () => true));
+        Assert.Equal(0, credits);
+    }
+}