1 files changed, 142 insertions, 0 deletions

diff --git a/Demos/Pong/Pong.hs b/Demos/Pong/Pong.hs
new file mode 100644
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+++ b/Demos/Pong/Pong.hs
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+module Pong
+  ( GameEvent (..),
+    GameObject,
+    newWorld,
+    stepWorld,
+    aabb,
+  )
+where
+
+import Data.Monoid (mconcat)
+import GHC.Float (double2Float)
+import Spear.Math.AABB
+import Spear.Math.Spatial2
+import Spear.Math.Vector
+import Spear.Step
+
+-- Configuration
+
+padSize = vec2 0.05 0.02
+
+ballSize = 0.01
+
+ballVelocity = vec2 0.3 0.3
+
+playerSpeed = 0.7
+
+initialEnemyPos = vec2 0.5 0.9
+
+initialPlayerPos = vec2 0.5 0.1
+
+initialBallPos = vec2 0.5 0.5
+
+-- Game events
+
+data GameEvent
+  = MoveLeft
+  | MoveRight
+  | StopLeft
+  | StopRight
+  deriving (Eq, Ord)
+
+-- Game objects
+
+data GameObject = GameObject
+  { aabb :: AABB2,
+    obj :: Obj2,
+    gostep :: Step [GameObject] [GameEvent] GameObject GameObject
+  }
+
+instance Spatial2 GameObject where
+  getObj2 = obj
+  setObj2 s o = s {obj = o}
+
+stepWorld :: Elapsed -> Dt -> [GameEvent] -> [GameObject] -> [GameObject]
+stepWorld elapsed dt evts gos = map (update elapsed dt evts gos) gos
+
+update :: Elapsed -> Dt -> [GameEvent] -> [GameObject] -> GameObject -> GameObject
+update elapsed dt evts gos go =
+  let (go', s') = runStep (gostep go) elapsed dt gos evts go
+   in go' {gostep = s'}
+
+ballBox, padBox :: AABB2
+ballBox = AABB2 (vec2 (-s) (-s)) (vec2 s s) where s = ballSize
+padBox = AABB2 (-padSize) padSize
+
+obj2 = obj2FromVectors unitx2 unity2
+
+newWorld =
+  [ GameObject ballBox (obj2 initialBallPos) $ stepBall ballVelocity,
+    GameObject padBox (obj2 initialEnemyPos) stepEnemy,
+    GameObject padBox (obj2 initialPlayerPos) stepPlayer
+  ]
+
+-- Ball steppers
+
+stepBall vel = collideBall vel .> moveBall
+
+collideBall :: Vector2 -> Step [GameObject] e GameObject (Vector2, GameObject)
+collideBall vel = step $ \_ dt gos _ ball ->
+  let (AABB2 pmin pmax) = aabb ball `aabbAdd` pos ball
+      collideCol = x pmin < 0 || x pmax > 1
+      collideRow = y pmin < 0 || y pmax > 1 || any (collide ball) (tail gos)
+      negx v@(Vector2 x y) = if collideCol then vec2 (-x) y else v
+      negy v@(Vector2 x y) = if collideRow then vec2 x (-y) else v
+      vel' = negx . negy $ vel
+      delta = dt -- A small delta to apply when collision occurs.
+      adjustX = if collideCol then scale delta (vec2 (x vel) 0) else vec2 0 0
+      adjustY = if collideRow then scale delta (vec2 0 (y vel)) else vec2 0 0
+   in ((vel' + adjustX + adjustY, ball), collideBall vel')
+
+collide go1 go2 =
+  let (AABB2 (Vector2 xmin1 ymin1) (Vector2 xmax1 ymax1)) =
+        aabb go1 `aabbAdd` pos go1
+      (AABB2 (Vector2 xmin2 ymin2) (Vector2 xmax2 ymax2)) =
+        aabb go2 `aabbAdd` pos go2
+   in not $
+        xmax1 < xmin2
+          || xmin1 > xmax2
+          || ymax1 < ymin2
+          || ymin1 > ymax2
+
+aabbAdd (AABB2 pmin pmax) p = AABB2 (p + pmin) (p + pmax)
+
+moveBall :: Step s e (Vector2, GameObject) GameObject
+moveBall = step $ \_ dt _ _ (vel, ball) -> (move (scale dt vel) ball, moveBall)
+
+-- Enemy stepper
+
+stepEnemy = movePad
+
+movePad :: Step s e GameObject GameObject
+movePad = step $ \elapsed _ _ _ pad ->
+  let p = vec2 px 0.9
+      px =
+        double2Float (sin elapsed * 0.5 + 0.5)
+          * (1 - 2 * x padSize)
+          + x padSize
+   in (setPos p pad, movePad)
+
+-- Player stepper
+
+stepPlayer = sfold moveGO .> clamp
+
+moveGO =
+  mconcat
+    [ switch StopLeft sid MoveLeft (moveGO' $ vec2 (-playerSpeed) 0),
+      switch StopRight sid MoveRight (moveGO' $ vec2 playerSpeed 0)
+    ]
+
+moveGO' :: Vector2 -> Step s e GameObject GameObject
+moveGO' dir = step $ \_ dt _ _ go -> (move (scale dt dir) go, moveGO' dir)
+
+clamp :: Step s e GameObject GameObject
+clamp = spure $ \go ->
+  let p' = vec2 (clamp' x s (1 - s)) y
+      (Vector2 x y) = pos go
+      clamp' x a b
+        | x < a = a
+        | x > b = b
+        | otherwise = x
+      (Vector2 s _) = padSize
+   in setPos p' go