1 files changed, 46 insertions, 0 deletions
diff --git a/src/LivingVillage.Kernel/Sim.fs b/src/LivingVillage.Kernel/Sim.fs
new file mode 100644
index 0000000..d1b2e57
--- /dev/null
+++ b/src/LivingVillage.Kernel/Sim.fs
@@ -0,0 +1,46 @@
+namespace LivingVillage.Kernel
+
+module Sim =
+
+    type Vec2 =
+        { X: float32
+          Y: float32 }
+
+    type Avatar =
+        { Pos: Vec2 }
+
+    type Input =
+        { MoveX: float32
+          MoveY: float32 }
+
+    type TimeStep =
+        { Dt: float32
+          Input: Input }
+
+    type World =
+        { Tick: int64
+          Avatar: Avatar }
+
+    let mapWidthTiles = 64
+    let mapHeightTiles = 48
+    let tilePixels = 32
+    let avatarSpeed = 160.0f
+
+    let initialWorld () : World =
+        let centerX = float32 (mapWidthTiles * tilePixels / 2 - tilePixels / 2)
+        let centerY = float32 (mapHeightTiles * tilePixels / 2 - tilePixels / 2)
+        { Tick = 0L
+          Avatar = { Pos = { X = centerX; Y = centerY } } }
+
+    let clamp v lo hi = if v < lo then lo elif v > hi then hi else v
+
+    let step (ts: TimeStep) (world: World) : World =
+        let maxX = float32 (mapWidthTiles * tilePixels - tilePixels)
+        let maxY = float32 (mapHeightTiles * tilePixels - tilePixels)
+        let dx = ts.Input.MoveX * avatarSpeed * ts.Dt
+        let dy = ts.Input.MoveY * avatarSpeed * ts.Dt
+        { Tick = world.Tick + 1L
+          Avatar =
+            { Pos =
+                { X = clamp (world.Avatar.Pos.X + dx) 0.0f maxX
+                  Y = clamp (world.Avatar.Pos.Y + dy) 0.0f maxY } } }