Shader grid transparent

shader_type canvas_item;
render_mode unshaded;

uniform float size = 10.0;
uniform float alpha = 1.0;
uniform vec4 color1 : hint_color = vec4(0.8431372549019608, 0.8431372549019608, 0.8431372549019608, 1.0);
uniform vec4 color2 : hint_color = vec4(1.0);
uniform vec2 offset = vec2(0.0);
uniform vec2 scale = vec2(0.0);
uniform vec2 rect_size = vec2(0.0);
uniform bool follow_movement = false;
uniform bool follow_scale = false;

void fragment() {
    vec2 ref_pos = FRAGCOORD.xy;
    if (follow_scale) {
        if (!follow_movement)
            ref_pos /= scale;
        else
            ref_pos = UV * rect_size;
    }
    else if (follow_movement)
        ref_pos -= mod(offset, size * 2.0);

    vec2 pos = mod(ref_pos, size * 2.0);
    bool c1 = any(lessThan(pos, vec2(size)));
    bool c2 = any(greaterThanEqual(pos, vec2(size)));
    float c = c1 && c2 ? 1.0: 0.0;
    COLOR = mix(color1, color2, c);
    COLOR.a = alpha;
}