```glsl
precision mediump float;

uniform float u_time;
uniform vec2 u_mouse;
uniform vec2 u_resolution;
varying vec2 v_uv;

float sdfTunnel(vec3 p) {
    float t = atan(p.x, p.z);
    float r = length(p.xz);
    return abs(r - 2.0 + 0.5 * sin(t * 8.0 + u_time * 2.0));
}

vec3 getColor(float t) {
    return 0.5 + 0.5 * cos(t + vec3(0.0, 2.0, 4.0));
}

void main() {
    vec2 uv = (v_uv - 0.5) * vec2(u_resolution.y / u_resolution.x, 1.0);
    vec3 ro = vec3(0.0, 0.0, -4.0);
    vec3 rd = normalize(vec3(uv, 1.0));

    float totalDist = 0.0;
    for (int i = 0; i < 100; i++) {
        vec3 p = ro + rd * totalDist;
        float dist = sdfTunnel(p);
        totalDist += dist;
        if (dist < 0.001 || totalDist > 10.0) break;
    }

    vec3 col = getColor(totalDist * 0.1);

    float mouseDist = distance(u_mouse, v_uv);
    col *= 1.0 + 0.5 * mouseDist;

    gl_FragColor = vec4(col, 1.0);

    #include <colorspace_fragment>
}
```