// Vogel Spiral By Frank Force
#define M iMouse
#define R iResolution
#define T iTime
#define pi 3.14
void mainImage(out vec4 fragColor,in vec2 fragCoord)
{vec2 m=(M.xy)/R.xy+.5,u=99.*m.x*(gl_FragCoord.rg-R.rg/2.)/R.r;
float d=pow(10.*length(u),.7),
t=.005*(T+200.*m.x),
i=floor(d-atan(u.g,u.r)/pi/2.+.5),
a=atan(u.g,u.r)+pi*2.*i,h=.002*a+1.5*t,
s=fract(a*.5*t)<.5?1.:0.,v=fract(a*t)<.5?0.:1.;
fragColor=vec4(vec3(v-s*v*.5)+vec3(s*v)*cos(pi*2.*(h+vec3(1.,.666,.333))),1.);}