precision mediump float;
varying vec2 a_pos;
uniform float u_time; //frames since page load
uniform float u_stime; //frames since shader compile
uniform vec2 u_mouse;
uniform vec2 u_resolution;
uniform vec4 u_date; //year, month, day, hour
void mainImage( out vec4 c, in vec2 fc )
{
vec2 uv = (2.0*gl_FragCoord.xy-u_resolution.xy)/u_resolution.y;
vec3 color = vec3(length(uv));
c = vec4(color,1.0);
}
void main(void) {
vec2 uv = a_pos;
mainImage(gl_FragColor, uv);
}