From 468d62dc27508a2c921a1ed1b285ed6ae43ca3c0 Mon Sep 17 00:00:00 2001
From: Lukas Krickl <lukas@krickl.dev>
Date: Thu, 27 Nov 2025 12:41:10 +0100
Subject: [PATCH] actor: Added basic collision check when moving

---
 src/actor.s  | 118 +++++++++++++++++++++++++++++++++++++++++++++++++++
 src/defs.s   |   1 +
 src/player.s |   5 +++
 src/tiles.s  |   2 +-
 4 files changed, 125 insertions(+), 1 deletion(-)

diff --git a/src/actor.s b/src/actor.s
index 74bf10e..e194775 100644
--- a/src/actor.s
+++ b/src/actor.s
@@ -1,4 +1,122 @@
+	; fixes y position
+	; inputs:
+	;		a: direction
+	;	 hl: ptr to y pos
+	;	returns:
+	;		fixed y pos
+	;		a is unchanged
+	;	 hl: += 1
+	;		b: y pos adjusted / 16
+_act_test_col_y:
+	push af
+	and a, DIRUP
+	jr nz, @up REL
+	
+	pop af
+	push af
+	and a, DIRDOWN
+	jr nz, @down REL
+	
+	; no change
+	ld a, [hl+]
+	div16 a
+	ld b, a
+
+	pop af
+	ret
+@up:
+	ld a, [hl+]
+	div16 a
+	dec a
+	ld b, a
+
+	pop af
+	ret
+@down:
+	ld a, [hl+]
+	div16 a
+	inc a
+	ld b, a
+
+	pop af
+	ret
+	
+	; fixes x positions
+	; inputs:
+	;		a: direction
+	;		hl: ptr to x pos
+	;	returns:
+	;		fixed x pos
+	;		a is unchanged
+	;		c: x pos adjusted / 16
+_act_test_col_x:
+	push af
+
+	and a, DIRLEFT
+	jr nz, @left REL
+	
+	pop af
+	push af
+	and a, DIRRIGHT
+	jr nz, @right REL
+
+	; no change
+	ld a, [hl]
+	div16 a
+
+	ld c, a
+	pop af
+	ret
+@left:
+	ld a, [hl]
+	div16 a
+	dec a
+	ld c, a
 	
+	pop af
+	ret
+@right:
+	ld a, [hl]
+	div16 a
+	inc a
+	ld c, a
+
+	pop af
+	ret
+	
+	; test collision based on an actor
+	; and a direction
+	;	inputs:
+	;		de: actor
+	;		 a: direction
+	;	returns:
+	;		a: new direction
+	;		a: 0 if move should be aborted
+act_test_collision:
+	push af
+
+	ld hl, act_pos_y
+	add hl, de
+
+	call _act_test_col_y
+	call _act_test_col_x
+
+	; b/c = y/x
+	call map_get_tile
+
+	ld de, t_flags
+	add hl, de
+	ld a, [hl]
+	and a, TF_WALL
+	jr nz, @collision REL
+
+	pop af
+	ret
+@collision:
+	pop af
+	ld a, 0
+	ret
+
 	; update routines for each actor
 actor_map_update_table:
 	
diff --git a/src/defs.s b/src/defs.s
index 6234d09..0343f35 100644
--- a/src/defs.s
+++ b/src/defs.s
@@ -104,6 +104,7 @@
 
 	; tile flags
 .se 1
+.de TF_WALL, 1
 
 	; tile struct
 .se 0 
diff --git a/src/player.s b/src/player.s
index ff68ce3..536f234 100644
--- a/src/player.s
+++ b/src/player.s
@@ -54,6 +54,11 @@ player_inputs:
 @notright:
 	ret
 @set:
+	ld de, player
+	call act_test_collision
+	cp a, 0
+	ret z
+
 	ld [player_direction], a
 	ld a, 16 ; tile size
 	ld [player_move_timer], a
diff --git a/src/tiles.s b/src/tiles.s
index 9014bfc..e383c9e 100644
--- a/src/tiles.s
+++ b/src/tiles.s
@@ -15,4 +15,4 @@ tile_grass:
 	tiledef TT_EMPTY, 0, GFX_GRASS
 
 tile_wall:
-	tiledef TT_WALL, 0, GFX_WALL
+	tiledef TT_WALL, TF_WALL, GFX_WALL
-- 
2.30.2