From 16c38fc10c7120bd86f69c25f179f7ed81262a70 Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Wed, 21 Jun 2023 23:01:18 +0100
Subject: Add "coyote time"

If the player moves and gains momentum, allow jumping then the gravity
as already kicked in to make easier tricky jumps.
---
 TODO.md      |  4 +++-
 src/player.c | 20 ++++++++++++++++++--
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/TODO.md b/TODO.md
index 92957ad..aacb433 100644
--- a/TODO.md
+++ b/TODO.md
@@ -3,7 +3,9 @@
 - entity system
   - free/used lists
 - player
-  - "coyote time"
+  - damage
+  - invulnerable
+  - respawn
 - map
   - entities
 - pick ups
diff --git a/src/player.c b/src/player.c
index 4fe916e..52595f4 100644
--- a/src/player.c
+++ b/src/player.c
@@ -25,10 +25,13 @@
 
 #define GRAVITY_SEQ_LEN 24
 
+/* used for "coyote time" */
+#define MAX_MOMENTUM 8
+
 #define IS_NOT_GOING_UP(x) (gravity == GRAVITY_OFF || (x)>=GRAVITY_DOWN)
 
 static uint16_t x, y;
-static uint8_t dir, frame, delay, gravity, jump;
+static uint8_t dir, frame, delay, gravity, jump, momentum;
 
 const uint8_t gravity_seq[GRAVITY_SEQ_LEN] = {
     6, 4, 4, 2, 2, 2, 2, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 2, 2, 2, 2, 4
@@ -72,6 +75,7 @@ void player_init(uint16_t start_x, uint8_t start_y)
     frame = FRAME_STANDING;
     delay = 0;
     jump = 0;
+    momentum = 0;
 
     x = start_x;
     y = start_y;
@@ -82,6 +86,9 @@ void player_update()
 {
     uint8_t moved = 0;
 
+    if (momentum)
+        momentum--;
+
     if (gravity == GRAVITY_OFF
             && !map_is_blocked(x + 4, y + 16)
             && !map_is_blocked(x + 11, y + 16))
@@ -93,9 +100,10 @@ void player_update()
 
     if (keys[KEY_UP])
     {
-        if (gravity == GRAVITY_OFF && !jump)
+        if ((gravity == GRAVITY_OFF || momentum) && !jump)
         {
             jump = 1;
+            momentum = 0;
             frame = FRAME_JUMPING;
             gravity = GRAVITY_UP;
         }
@@ -115,7 +123,11 @@ void player_update()
                     || (!IS_NOT_GOING_UP(gravity)
                         && !(map_is_blocked(x + 16, y + 15)
                              && map_is_blocked(x + 16, y + 7))))
+            {
+                if (gravity == GRAVITY_OFF && momentum < MAX_MOMENTUM)
+                    momentum += 4;
                 x++;
+            }
         }
     }
 
@@ -131,7 +143,11 @@ void player_update()
                     || (!IS_NOT_GOING_UP(gravity)
                         && !(map_is_blocked(x - 1, y + 15)
                              && map_is_blocked(x - 1, y + 7))))
+            {
+                if (gravity == GRAVITY_OFF && momentum < MAX_MOMENTUM)
+                    momentum += 4;
                 x--;
+            }
         }
     }
 
-- 
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