Bouncing color gradient columns

bouncing-color-grad-bars.glsl

//Base on Tutorial #17, https://www.shadertoy.com/view/Md23DV
#define PI 3.14159265359

void main() {
  //coordinate systems
  vec2 r = vec2((gl_FragCoord.xy - 0.5*resolution.xy)/resolution.y) * 2.0; // Is [-1, 1] coordinate system
  vec2 p = vec2(gl_FragCoord.xy/resolution.xy); //[0,1] coordinate system
  
  //Set background color
  vec3 bgCol = vec3(0.0); // black
  vec3 pixel = bgCol;
  
  vec3 rAxesColor = vec3(0.537, 1.0, 0.364);
  float rAxesThickness = 0.006;
  
  vec3 pAxesColor = vec3(1.0, 0.412, 0.635);
  float pAxesThickness = 0.008;
  
  // -----------------------------------
  // ------------ Start ----------------
  
  vec3 col1 = vec3(0.216, 0.471, 0.698); // blue
  vec3 col2 = vec3(1.00, 0.329, 0.298); // red
  vec3 col3 = vec3(0.867, 0.910, 0.247); // yellow
  
  float item0;
  float item1;
  float pctMix;
  float mixedVal;
  vec3 ret;
  
  if(p.x < 1.0/5.0){
  	pctMix = smoothstep(0.25*abs(1.5*sin(time)+0.25), 0.75*abs(1.5*sin(time)+0.25), p.y);
    ret = mix(col1, col2, pctMix);
  }
  else if(p.x < 2.0/5.0) { // Part II
    pctMix = smoothstep(0.25*abs(2.0*sin(time)+0.5), 0.75*abs(2.0*sin(time)+0.5), p.y);
    ret = mix(col1, col2, pctMix);
  }
  else if(p.x < 3.0/5.0) {
  	pctMix = smoothstep(0.25*abs(0.65*sin(time)+0.75), 0.85*abs(0.5*sin(time)+0.75), p.y);
    ret = mix(col1, col2, pctMix);
  }
  else if(p.x < 4.0/5.0){
  	pctMix = smoothstep(0.25*abs(sin(time)+1.25), 0.75*abs(sin(time)+1.25), p.y);
    ret = mix(col1, col2, pctMix);
  }
  else {
  	pctMix = smoothstep(0.15*abs(sin(time)), 0.95*abs(sin(time)), p.y);
    ret = mix(col1, col2, pctMix);
  }
  
  pixel = vec3(ret);
 
  // ------------- End -----------------
  // -----------------------------------
  
  //[0,1] coordinat system axes
  if(abs(p.x) < pAxesThickness) pixel = pAxesColor;
  if(abs(p.y) < pAxesThickness) pixel = pAxesColor;
  
  //[-1,1] coordinat system axes
  // if(abs(r.x) < rAxesThickness) pixel = rAxesColor;
  // if(abs(r.y) < rAxesThickness) pixel = rAxesColor;
  
  //Final output
  gl_FragColor = vec4(pixel, 1.0);
}