function parameters
x, y = position of pixel
t = current time (ms)
d = imageData array
r, g, b, a = color values

Math aliases
floor, ceil, round, abs, sign
pow, exp, sqrt
sin, cos, tan
asin, acos, atan, atan2
random()
E, PI

convenience functions
clamp(n,min,max)
lerp(n,a,b)
mix(n,a,b)
step(n,a,b)
smoothstep(n,a,b)
sinp, cosp (mapped to [0,1])
pixel(x,y) == 4*(y*w+h)
rand(n), randint(n)
choice(array)
deg(radians), rad(degrees)