shader_type canvas_item;
render_mode skip_vertex_transform;

uniform vec4 color_1 : hint_color = vec4(1.0, 1.0, 1.0, 1.0);
uniform vec4 color_2 : hint_color = vec4(0.0, 0.0, 0.0, 1.0);
uniform vec2 checker_size = vec2(8.0, 8.0);
uniform vec2 cycle_speed = vec2(0.0, 0.0);
uniform vec2 pan_speed = vec2(0.0, 0.0);
uniform mat4 uv_transform = mat4(1.0);

float checker(vec2 uv) {
	vec2 div_uv = floor((uv) / checker_size);
	float fmodResult = mod(div_uv.x + div_uv.y, 2.0);
	return max(sign(fmodResult), 0.0);
}

void vertex() {
	UV = VERTEX;
    VERTEX = (WORLD_MATRIX * (EXTRA_MATRIX * vec4(VERTEX, 0.0, 1.0))).xy;
}

void fragment() {
	vec2 uv = UV - pan_speed * TIME;
	uv = (uv_transform * vec4(uv, 0.0, 1.0)).xy;
	uv -= cycle_speed * TIME;
	COLOR = mix(color_1, color_2, checker(uv));
}