WebGL Lab.
// title: SinCurve

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;

void main(){
  vec3 color=vec3(0.);
  const float count=25.;
  vec2 g=gl_FragCoord.xy/u_resolution.xy;
  for(float i=0.;i<count;i++){
    float siny=.5+.25*sin(2.*3.14*g.x+u_time+.2*i);
    float curve=siny-g.y;
    if(curve>=0.&&curve<.01){
      color+=vec3(g.x,g.y,g.x*g.y+i/count);
    }
  }
  gl_FragColor=vec4(color,1.);
}