From: Lukas Krickl <lukas@krickl.dev>
Date: Sat, 20 Sep 2025 07:10:16 +0000 (+0200)
Subject: player: Added basic movement
X-Git-Url: https://git.krickl.dev/?a=commitdiff_plain;h=6eec856f7e29684c45aa7e515c9dbe6e9f4333f5;p=gbrg%2F.git

player: Added basic movement
---

diff --git a/src/player.s b/src/player.s
index 4a3147e..31e966c 100644
--- a/src/player.s
+++ b/src/player.s
@@ -1,3 +1,5 @@
+#define PLAYER_SPEED 1
+
 	; sets up the player actor
 player_init:
 	; initial position
@@ -12,9 +14,108 @@ player_init:
 	
 	; updates the special player actor
 player_update:
+	ld b, BTNUP
+	input_held
+	jr z, @not_up REL
+		ld b, PLAYER_SPEED
+		ld c, 0
+		call player_stage_move_n
+		call player_try_move
+@not_up:
+
+	ld b, BTNDOWN
+	input_held
+	jr z, @not_down REL
+		ld b, PLAYER_SPEED
+		ld c, 0
+		call player_stage_move_p
+		call player_try_move
+
+@not_down:
+
+	ld b, BTNLEFT
+	input_held
+	jr z, @not_left REL
+		ld b, 0 
+		ld c, PLAYER_SPEED 
+		call player_stage_move_n
+		call player_try_move
+@not_left:
+
+	ld b, BTNRIGHT
+	input_held
+	jr z, @not_right REL
+
+		ld b, 0
+		ld c, PLAYER_SPEED
+		call player_stage_move_p
+		call player_try_move
+@not_right:
+
 	ret
 
 #define PLAYER_SPRITE_IDLE1 0x8D
+	
+	; stages a move in a positive directon
+	; inputs:
+	;		b/c: y/x movement
+	;	returns:
+	;		b/c: new y/x position
+	;		  d: new y hi position
+player_stage_move_p:
+	ld a, [player+act_pos_y]
+	add a, b
+	ld b, a
+
+	ld a, [player+act_pos_y_hi]
+	adc a, 0
+	ld [player+act_pos_y_hi], a
+	ld d, a
+
+	ld a, [player+act_pos_x]
+	add a, c
+	ld c, a
+	
+	ret
+
+	; stages a move in a negative directon
+	; inputs:
+	;		b/c: y/x movement
+	;	returns:
+	;		b/c: new y/x position
+	;		  d: new y hi position
+player_stage_move_n:
+	ld a, [player+act_pos_y]
+	sub a, b
+	ld b, a
+
+	ld a, [player+act_pos_y_hi]
+	sbc a, 0
+	ld [player+act_pos_y_hi], a
+	ld d, a
+
+	ld a, [player+act_pos_x]
+	sub a, c
+	ld c, a
+	
+	ret
+	
+	; moves the player
+	; performs a collision check
+	; moves scroll and performs map loads if needed
+	; inputs:
+	;		b/c: new y/x position
+	;		d: new y hi position
+player_try_move:
+	ld a, b
+	ld [player+act_pos_y], a
+
+	ld a, c
+	ld [player+act_pos_x], a
+
+	ld a, d
+	ld [player+act_pos_y_hi], a
+	ret
 
 	; draws the special player actor
 player_draw: