PPOBC tutorial code.txt

var sprite_bbox_top = sprite_get_bbox_top(sprite_index)-sprite_get_yoffset(sprite_index);
var sprite_bbox_bottom = sprite_get_bbox_bottom(sprite_index)-sprite_get_yoffset(sprite_index)+1;
var sprite_bbox_left = sprite_get_bbox_left(sprite_index)-sprite_get_xoffset(sprite_index);
var sprite_bbox_right = sprite_get_bbox_right(sprite_index)-sprite_get_xoffset(sprite_index)+1;

//Snap coordinates
snap_x = 0;
snap_y = 0;

//Horizontal
for(var h=0;h<=ceil(abs(hspd));h++) {
	var wall_x = collision_real_id(h*sign(hspd),0,oWall);
	if wall_x != noone {
		var wall_left = wall_x.bbox_left;
		var wall_right = wall_x.bbox_right;
		if x < wall_left {//right
			snap_x = wall_left-sprite_bbox_right;
		} else if x > wall_right {//left
			snap_x = wall_right-sprite_bbox_left;
		}
		hspd = 0;
	}
}

//Vertical
for(var v=0;v<=ceil(abs(vspd));v++) {
	var wall_y = collision_real_id(0,v*sign(vspd),oWall);
	if wall_y != noone {
		var wall_top = wall_y.bbox_top;
		var wall_bottom = wall_y.bbox_bottom;
		if y < wall_top {//down
			snap_y = wall_top-sprite_bbox_bottom;
		} else if y > wall_bottom {//up
			snap_y = wall_bottom-sprite_bbox_top;
		}
		vspd = 0;
	}
}

x += hspd;
y += vspd;
if snap_x != 0 x = snap_x;
if snap_y != 0 y = snap_y;