gradient shader 2

// Author: Jeremy Rotsztain
// Course: ShaderArt (DIGF-3011, Winter 2022)
// Title: Hello World (GLSL)

// Edited by: Amanda Huynh Feb 16 2022

// ignore this for the time being
#ifdef GL_ES
precision mediump float;
#endif

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

void main() {

    // get the xy coordinate in pixels & normalize to [0, 1] range
    // by dividing by width (500 x 500 px)
    vec2 st = gl_FragCoord.xy/u_resolution.xy;

    //  position in a bit higher than center
    // https://thebookofshaders.com/07/
    float pct = 0.0;
    pct = distance(st,vec2(0.500,0.700));

    // fix for aspect ratio
    st.x *= u_resolution.x/u_resolution.y;

    vec3 color = vec3(pct);

    // red as sinusodal curve positioned pct
    color.r = sin(u_time-pct* 1.5)*3.128;

    // // center blue, mouse interaction
    color.b = sin(u_mouse.x/u_resolution.x+pct);

    // // green as fract
    color.g = fract(u_time-pct *15.*-st.y);

//     RGBA
    gl_FragColor = vec4(color,1.);
}