Use fixed-point number to store Y coordinate

src/player.s

@@ -10,7 +10,7 @@ playerWorldY: dw
 
 ; player data
 PLAYER_X:: db
-PLAYER_Y:: db
+PLAYER_Y:: dw
 PLAYER_DIR:: db
 
 PLAYER_JUMPING:: db
@@ -44,6 +44,8 @@ Player_Init::
     ld [hl], 0
     inc hl
     ld [hl], 0
+    inc hl
+    ld [hl], 0
 
     ; Copy sprite to VRAM
     ld bc, _VRAM8000 + SPRITE_IDX * 16
@@ -104,9 +106,12 @@ Player_Update::
     STORE16 bc
 
     ; y -= floor(vy)
-    ld hl, PLAYER_Y
+    ld hl, PLAYER_Y + 1
+    ld a, [hl]
+    sub c
+    ld [hl-], a
     ld a, [hl]
-    sub b
+    sbc b
     ld [hl], a
 
     ; roll back jump if there was a collision
@@ -216,6 +221,7 @@ update_oam:
     and OAMF_XFLIP
     ld c, a
 
+    dec hl ; skip fractional part
     ld a, [hl-] ; y
     add 16