From 54d3f5a32758eb92606338d28a13652bcf51375c Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Tue, 7 Feb 2023 12:10:02 +0000
Subject: Implemented "Coyote time" to make jumping easier

---
 src/Game/Entities.hs | 55 ++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 47 insertions(+), 8 deletions(-)

diff --git a/src/Game/Entities.hs b/src/Game/Entities.hs
index 66d2da6..b42f232 100644
--- a/src/Game/Entities.hs
+++ b/src/Game/Entities.hs
@@ -1,5 +1,3 @@
-{-# OPTIONS_GHC -Wno-unused-top-binds #-}
-
 module Game.Entities (Entities, mkEntities, mkPlayer, mkEffect, append, update, render) where
 
 import Data.Foldable (traverse_)
@@ -29,7 +27,10 @@ gravityUp :: Int
 gravityUp = 0
 
 gravityDown :: Int
-gravityDown = 16
+gravityDown = 14
+
+jumpLimit :: Int
+jumpLimit = gravityDown + 7
 
 gravityTable :: [Int]
 gravityTable = [0, 6, 4, 4, 2, 2, 2, 2, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 2, 2, 2, 2, 4]
@@ -45,6 +46,7 @@ data Entity = Entity
     eDelay :: Int,
     eFrame :: Int,
     eFrameLimit :: Int,
+    eJumping :: Bool,
     eGravity :: Int,
     eDir :: Dir,
     eSprite :: S.Sprite,
@@ -86,7 +88,23 @@ render renderer (Entities _ entities) = do
 mkEffect :: S.SpriteSheet -> Int -> Int -> String -> IO Entity
 mkEffect sprites x y name = do
   s <- S.get sprites name
-  pure $ Entity TypeEffect x y frameDelay 0 3 gravityOff DirRight s (pure . updateEffect) (\_ _ -> False) False []
+  pure $
+    Entity
+      { eType = TypeEffect,
+        eX = x,
+        eY = y,
+        eDelay = frameDelay,
+        eFrame = 0,
+        eFrameLimit = 3,
+        eJumping = False,
+        eGravity = gravityOff,
+        eDir = DirRight,
+        eSprite = s,
+        eUpdate = pure . updateEffect,
+        eBlocked = \_ _ -> False,
+        eDestroy = False,
+        eSpawns = []
+      }
 
 updateEffect :: Entity -> Entity
 updateEffect e
@@ -101,7 +119,23 @@ updateEffect e
 mkPlayer :: S.SpriteSheet -> Int -> Int -> IORef C.Controls -> (Int -> Int -> Bool) -> IO Entity
 mkPlayer sprites x y controls isBlocked = do
   s <- S.get sprites "player"
-  pure $ Entity TypePlayer x y 0 0 3 gravityOff DirRight s (updatePlayer controls) isBlocked False []
+  pure $
+    Entity
+      { eType = TypePlayer,
+        eX = x,
+        eY = y,
+        eDelay = 0,
+        eFrame = 0,
+        eFrameLimit = 3,
+        eJumping = False,
+        eGravity = gravityOff,
+        eDir = DirRight,
+        eSprite = s,
+        eUpdate = updatePlayer controls,
+        eBlocked = isBlocked,
+        eDestroy = False,
+        eSpawns = []
+      }
 
 updateFrame :: Bool -> Entity -> Entity
 updateFrame updated e
@@ -136,8 +170,12 @@ updateHorizontal left right e
 
 updateVertical :: Bool -> Bool -> Entity -> Entity
 updateVertical jump down e
-  | not jump || gravity /= gravityOff = e
-  | not down = e {eGravity = gravityUp, eFrame = jumpFrame, eSpawns = events ++ [DustEffectSpawn x (y + 8)]}
+  | not jump
+      || jumping
+      -- make jumping easier with "Coyote time"
+      || (gravity /= gravityOff && (gravity < gravityDown || gravity > jumpLimit)) =
+      e
+  | not down = e {eJumping = True, eGravity = gravityUp, eFrame = jumpFrame, eSpawns = events ++ [DustEffectSpawn x (y + 8)]}
   -- go down a 8 pixel tall platform; not ideal to have these values hardcoded here
   -- but to be fair, the player height/width is hardcoded as well
   | down
@@ -148,6 +186,7 @@ updateVertical jump down e
   where
     x = eX e
     y = eY e
+    jumping = eJumping e
     gravity = eGravity e
     isBlocked = eBlocked e
     events = eSpawns e
@@ -160,7 +199,7 @@ applyGravity v e
       && (isBlocked (x + 2) (y + 24) || isBlocked (x + 12) (y + 24))
       && not (isBlocked (x + 2) (y + 23))
       && not (isBlocked (x + 12) (y + 23)) =
-      e {eGravity = gravityOff, eDelay = 0}
+      e {eJumping = False, eGravity = gravityOff, eDelay = 0}
   | otherwise = applyGravity (v - 1) e {eY = y + change}
   where
     gravity = eGravity e
-- 
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