Own reflections

Multiplying a color with a value makes the color brighter or darker.

Adding a color with a value makes the color brighter.

Subtracting a color with a value makes the color darker.

fract(u_time) gives back a values that moves from 0.0 -> 1.0 and starts again at 0.0

To specify to which value it modulates you can use float m = mod(u_time,.5).

Mirror effect

If you move the uv by 0.5 into the center and then use abs() you can create a kaleido/mirror effect.

vec2 uv = gl_FragCoord.xy/u_resolution;
uv -= vec2(0.5);
uv = abs(uv)

Invert colors/values

If you want to invert the colors that you have you can substract your color/value from 1.0 float invertValue = 1.0 - value vec3 invColor = vec3(1.0) - color

If you want to test if a value is smaller than a threshold value you can subtract the value from 1.0

val = step(0.2,0.5) returns 1.0 -> true
1.0 - val = 0 -> false

val2 = step(0.8,0.5) = 0 -> false
1.0 - val = 1 -> true

Coloring

To color you can for example calculate the distance field or the shaper and then just multiply it with a color vec3 or use mix(color1,color2, shape)

Abs Function

Using abs on coordinates creates symmetry around axes when we moved the canvas coord system to the center.