Reverse Engineering Code Art - Part 2

Analyzing The eye of the storm

Original Dwitter by cantelope

TLDR

eval(unescape(escape`𩡯𬠨𪐽𪀽𝐴𜀬𣰽𬐽🠨𣑡𭁨𛡲𨑮𩁯𫐨𚐪𜠭𜐩𚡷𞱩𛐭𞱸𛡣𫁥𨑲𤡥𨱴𚁨𚱩𙐲𚠴𝐬𜠵𝠫𚁩𙐴𛰲𯀰𚐪𞐰𛀳𝐬𞀰𚐩𮀮𩡩𫁬𤡥𨱴𚁘🐨𭰽𞐶𜀩𚱏𚀩𛁙👨𚱏𚀩𛁳👷𛰨𭀥𞀩𛰹𛁳𛁸𛡦𪑬𫁓𭁹𫁥👠𪁳𫀨𜐵𜀠𞐹𙐤𮰨𣑡𭁨𛡨𮑰𫱴𚁘𛑷𛁙𛑨𚐯𜐸𜀩𚠪𜱽𙑠𚐻`.replace(/u../g,'')))

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The whole code is in Unicode, this is to reduce the size of the whole code. Let’s evaluate the Unicode to utf-8

for(i=h=540,O=q=>(Math.random()*2-1)*w;i--;x.clearRect(h+i%2*45,256+(i%4/2|0)*90,35,80))x.fillRect(X=(w=960)+O(),Y=h+O(),s=w/(t%8)/9,s,x.fillStyle=`hsl(150 99%${(Math.hypot(X-w,Y-h)/180)**3}%`);

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Much better, now let’s start analyzing it

for (
  i = h = 540, O = (q) => (Math.random() * 2 - 1) * w;
  i--;
  x.clearRect(h + (i % 2) * 45, 256 + (((i % 4) / 2) | 0) * 90, 35, 80)
)
  x.fillRect(
    (X = (w = 960) + O()),
    (Y = h + O()),
    (s = w / (t % 8) / 9),
    s,
    (x.fillStyle = `hsl(150 99%${(Math.hypot(X - w, Y - h) / 180) ** 3}%`)
  )

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Rearranging things to make it look readable.

There are some JS tricks I ran into used to obscure the code

• (w = 960) + O() is simply 960 + O() with w initialized
• In the function O=q=>(Math.random()*2-1)*w; even though the param q is not used, we have a param as q is 1 char compared to () 2 chars
• Math.hypot(X, Y) to save space instead of (X**2 + Y**2)**0.5

const w = 960;
const h = 540;
const O = () => (Math.random() * 2 - 1) * w;

for (let i = h; i--; ) {
  const X = w + O();
  const Y = h + O();
  const s = w / (t % 8) / 9;

  x.fillStyle = `hsl(150 99%${(Math.hypot(X - w, Y - h) / 180) ** 3}%`;
  x.fillRect(X, Y, s, s);
  x.clearRect(h + (i % 2) * 45, 256 + (((i % 4) / 2) | 0) * 90, 35, 80); // Lens flare
}

Now for the math

Summary

• w is the width of the eye of the storm
• O = () => (Math.random() * 2 - 1) * w; gives value from [-w, w]
• Using the O() a random X and Y is calculated
• x.clearRect is used to give the lens flare effect
• Math.hypot(X - w, Y - h) / 180) ** 3 is used to calculate the lightness in hsl(distance from center)
• s is the size of the pixel, t % 8 so the size varies with time to give the blur effect