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HTML

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CSS

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CSS Base

About CSS Base

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                p Click anywhere on the grid to start, but the top right corner is the best spot. And you need to have 'Experimental Web Platform Features' flag enabled to make it working 🤷‍♂️

- var n = 20;

mixin child(pos, limit)
  if limit
    span(class='a' + (Math.floor((limit - 1) / n) % 2 === 1 ? 'a' : '') + (pos+1), tabindex=1)
      +child((pos + 1) % n, limit - 1)

.container
  +child(0, n * n)
!

CSS 

              
                $size: 30px;
$n: 20;

.container {
  width: $size * $n;
}

:root {
  @for $i from 1 through $n {
    --a-#{$i}: 0;
    --aa-#{$i}: 0;
  }
}

// 110, 101, 011, 010, 001 => 1
// 111, 100, 000 => 0
// xyz || x!y!z || !x!y!z == xyz || !y!z

@for $i from 1 through $n {
  span.aa#{$i} {
    // Long and not efficient
    // --aa-#{$i}: calc(
    //   var(--a-#{$i - 1}, 0) * var(--a-#{$i}, 0) * (1 - var(--a-#{$i + 1}, 0)) +
    //   var(--a-#{$i - 1}, 0) * (1 - var(--a-#{$i}, 0)) * var(--a-#{$i + 1}, 0) +
    //   (1 - var(--a-#{$i - 1}, 0)) * var(--a-#{$i}, 0) * var(--a-#{$i + 1}, 0) +
    //   (1 - var(--a-#{$i - 1}, 0)) * var(--a-#{$i}, 0) * (1 - var(--a-#{$i + 1}, 0)) +
    //   (1 - var(--a-#{$i - 1}, 0)) * (1 - var(--a-#{$i}, 0)) * var(--a-#{$i + 1}, 0),
    //   0
    // );
    
    // Short and efficient
    --aa-#{$i}: calc(1 - (
      var(--a-#{$i - 1}, 0) * var(--a-#{$i}, 0) * var(--a-#{$i + 1}, 0) +
      (1 - var(--a-#{$i}, 0)) * (1 - var(--a-#{$i + 1}, 0))
      0)
    );
  }
  span.a#{$i} {
    // Long and not efficient
    // --a-#{$i}: calc(
    //   var(--aa-#{$i - 1}, 0) * var(--aa-#{$i}, 0) * (1 - var(--aa-#{$i + 1}, 0)) +
    //   var(--aa-#{$i - 1}, 0) * (1 - var(--aa-#{$i}, 0)) * var(--aa-#{$i + 1}, 0) +
    //   (1 - var(--aa-#{$i - 1}, 0)) * var(--aa-#{$i}, 0) * var(--aa-#{$i + 1}, 0) +
    //   (1 - var(--aa-#{$i - 1}, 0)) * var(--aa-#{$i}, 0) * (1 - var(--aa-#{$i + 1}, 0)) +
    //   (1 - var(--aa-#{$i - 1}, 0)) * (1 - var(--aa-#{$i}, 0)) * var(--aa-#{$i + 1}, 0),
    //   0
    // );
    
    // Short and efficient
    --a-#{$i}: calc(1 - (
      var(--aa-#{$i - 1}, 0) * var(--aa-#{$i}, 0) * var(--aa-#{$i + 1}, 0) +
      (1 - var(--aa-#{$i}, 0)) * (1 - var(--aa-#{$i + 1}, 0))
      0)
    );
  }
}

span::before {
  height: $size;
  width: $size;
  display: inline-block;
  box-sizing: border-box;
  text-align: center;
  line-height: $size;
  content: '・';
  background: black;
  color: white;
  border: 1px solid gray;
}

// The way to indicate the result
@for $i from 1 through $n {
  span.a#{$i}::before {
    --l: calc(1 - var(--a-#{$i}, 0));
    background: hsl(0, 0%, calc(100% * var(--l)));
  }
  span.aa#{$i}::before {
    --l: calc(1 - var(--aa-#{$i}, 0));
    background: hsl(0, 0%, calc(100% * var(--l)));
  }
  
  span.a#{$i}:focus {
    --a-#{$i}: 1;
  }
  span.aa#{$i}:focus {
    --aa-#{$i}: 1;
  }
}
!

JS 

              
                // Don't blame me, we'll have CSS syntax for that in future:
// https://github.com/w3c/css-houdini-drafts/issues/137#issuecomment-433037224
for (var i=1; i++; i<=20) {
  CSS.registerProperty({
    name: '--a-' + i,
    syntax: '<number>',
    inherits: true,
    initialValue: 0
  });
  CSS.registerProperty({
    name: '--aa-' + i,
    syntax: '<number>',
    inherits: true,
    initialValue: 0
  });
}
!
999px

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