shader_type canvas_item;

uniform float screen_height = 640.0;
uniform float amplitude = 0.075;
uniform float frequency = 10.0;
uniform float speed = 2.0;
uniform float amplitude_vertical = 0.0;
uniform float frequency_vertical = 0.0;
uniform float speed_vertical = 0.0;
uniform vec2 scroll_direction = vec2(0.0, 0.0);
uniform float scrolling_speed = 0.08;
uniform bool enable_palette_cycling = false;
uniform sampler2D palette;
uniform float palette_speed = 0.1;

void fragment() {
	float diff_x = amplitude * sin((frequency * UV.y) + (speed * TIME));
	float diff_y = amplitude_vertical * sin((frequency_vertical * UV.y) + (speed_vertical * TIME));
	vec2 scroll = scroll_direction * TIME * scrolling_speed;
	vec4 tex = texture(TEXTURE, vec2(UV.x + diff_x, UV.y + diff_y) + scroll);
	float palette_swap = mod(tex.r + TIME * palette_speed, 1.0);
	
	if (enable_palette_cycling)
	{
		COLOR = vec4(texture(palette, vec2(palette_swap, 0)).rgb, tex.a);
	}
	else COLOR = tex;
	
	COLOR = mix(vec4(0.0), COLOR, float(int(UV.y * screen_height) % 2));
}