TIC-80 Perlin Noise.js

// title:  Perlin Noise
// author: Anastasia Dunbar
// script: js
var width=240,height=136;
function mix(a,b,t){return(t*(b-a))+a;}
function mod(a,b){return((a%b)+b)%b;}
function fract(x){return x-Math.floor(x);}
function clamp(a,b,c){return Math.min(Math.max(a,b),c);}
function dot(a,b){for(var s=0,i=0;i<a.length;i++){s+=a[i]*b[i];}return s;}
function sign(x){return x>0?1:x<0?-1:0;}
function pow2(a,b){return Math.pow(Math.abs(a),b)*sign(a);}
function pal(i,r,g,b){
	i=i<0?0:i;i=i>15?15:i;
	if(r==undefined&&g==undefined&&b==undefined){return[peek(0x3fc0+(i*3)),peek(0x3fc0+(i*3)+1),peek(0x3fc0+(i*3)+2)];}else{
		poke(0x3fc0+(i*3)+2,clamp(b,0,255));poke(0x3fc0+(i*3)+1,clamp(g,0,255));poke(0x3fc0+(i*3),clamp(r,0,255));
	}
}
var seed={
	a:500+(Math.random()*1e4),
	fx:500+(Math.random()*1e4),
	fy:500+(Math.random()*1e4),
	px:Math.random()-.5,
	py:Math.random()-.5
}
function pseudorandom2D(x,y){return fract(Math.sin(dot([x+seed.px,y+seed.py],[seed.fx,seed.fy]))*seed.a);}
function perlin(x,y){
	return mix(
		mix(
			pseudorandom2D(Math.floor(x)  ,Math.floor(y)),
			pseudorandom2D(Math.floor(x)+1,Math.floor(y)),
			fract(x)
		),
		mix(
			pseudorandom2D(Math.floor(x)  ,Math.floor(y)+1),
			pseudorandom2D(Math.floor(x)+1,Math.floor(y)+1),
			fract(x)
		),
		fract(y)
	)
}
function f(x,y){
	x/=15;y/=15;
	var iterations=4,sum=0;
	for(var i=0;i<iterations;i++){
		seed.a=500+((fract(Math.sin((i+.512)*512)*725.63))*1e4);
		sum+=perlin(x*(i+1),y*(i+1));
	}
	return sum/iterations;
}
cls(0);
var i=0,stop=false,t=0,
s=function(x){return(Math.sin(x/6)+2)/3;},
r=function(){
	for(var j=0;j<16;j++){
		pal(
			j,
			~~((pow2(j/15,s(t)))*255),
			~~((pow2(j/15,s(t/2)))*255),
			~~((pow2(j/15,s(t/3)))*255)
		);
	}
};
function scanline(){
	if(stop){
		r();
		t+=1;
	}
}
function TIC(){
	if(!stop){
		for(var j=0;j<100;j++){
			if(i<width*height){
				var x=i%width,y=Math.floor(i/width);
				pix(x,y,Math.floor(clamp(f(x,y),0,1)*16));
				i++;
			}else{
				stop=true;
			}
		}
		r();
		t+=.5;
	}
}