Tangerine

precision highp float;

uniform vec2 u_resolution;
uniform float u_time;

float rand(vec2 co) {
    return fract(sin(dot(co, vec2(12.9898, 78.233))) * 43758.5453);
}

void main() {
    vec2 uv = gl_FragCoord.xy / u_resolution.xy;

    float waveCenter = 0.3
        + 0.05 * sin(u_time/2. + uv.x * 4.0)
        + 0.03 * sin(u_time/2. * 1.7 + uv.x * 7.0);

    float wC = 0.3 + 0.05 * sin(u_time + uv.x * 8.0) + 0.03 * sin(u_time * 0.7 + uv.x * 4.0);

    float bandStart = waveCenter - 0.025;  // Lower boundary for the gradient
    float bandEnd   = waveCenter + 0.025;  // Upper boundary for the gradient

    float bS = wC - 0.2;
    float bE   = wC + 0.2;

    float t = smoothstep(bandStart , bandEnd, uv.y);
    float s = smoothstep(bS, bE, uv.y);
    t = t * s;

    vec3 orange = vec3(1.0, 0.3, 0.0);
    vec3 black  = vec3(0.0);

    vec3 lightOrange = vec3(1.0, 0.6, 0.);  // Lighter orange
    vec3 redderOrange = vec3(1.0, 0.1, 0.0);   // Redder orange

    float mixFactor = 0.8 + 0.2 * sin(u_time + uv.x * 5.0);

    vec3 dO = mix(lightOrange, redderOrange, mixFactor);

    vec3 color = mix(dO, black, t);

    float noise = (rand(gl_FragCoord.xy) - 0.5) * 0.05; // adjust 0.1 to change intensity
    color += noise;

    gl_FragColor = vec4(color, 1.0);
}