shader_type spatial;

// unshaded matches the pixel-art look of the rest of the game.
// Opaque render mode guarantees the floor draws before any transparent Sprite3D /
// AnimatedSprite3D, which are always sorted into the transparent queue after opaque geo.
render_mode unshaded, depth_draw_opaque, cull_back;

// Texture carried over from the TrenchBroom surface material by acidarea.gd.
// hint_default_white means a flat white is used if nothing is assigned, so
// acid_color alone still produces a visible result.
uniform sampler2D albedo_tex : source_color, filter_nearest, repeat_enable, hint_default_white;
// Grayscale noise for UV distortion and bubble pulse. Falls back to white (no distortion).
uniform sampler2D noise_tex : hint_default_white, filter_linear_mipmap, repeat_enable;

uniform vec4 acid_color : source_color = vec4(0.2, 0.85, 0.1, 1.0);
uniform vec2 flow_direction = vec2(0.3, 0.15);
// How strongly the noise warps the UV coords
uniform float distortion_strength = 0.04;
// Additive glow tint strength (0 = no glow)
uniform float emission_energy = 0.4;

void fragment() {
	vec2 uv = UV;
	float t = TIME;

	// Sample noise at two offsets to build a swirling distortion field
	vec2 noise_uv_a = uv * 0.5 + vec2(t * 0.05, t * 0.03);
	vec2 noise_uv_b = uv * 0.5 + vec2(-t * 0.04, t * 0.06);
	float noise_a = texture(noise_tex, noise_uv_a).r;
	float noise_b = texture(noise_tex, noise_uv_b).r;
	vec2 distortion = vec2(noise_a, noise_b) * 2.0 - 1.0;

	vec2 scrolled_uv = uv + flow_direction * t + distortion * distortion_strength;

	vec4 tex_color = texture(albedo_tex, scrolled_uv);
	vec3 final_color = tex_color.rgb * acid_color.rgb;

	// Subtle additive glow pulsing with noise so the surface looks alive
	float bubble_pulse = texture(noise_tex, uv * 0.3 + vec2(t * 0.1)).r;
	final_color += final_color * emission_energy * (0.7 + 0.3 * bubble_pulse);

	ALBEDO = final_color;
}