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HTML

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CSS

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CSS Base

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                form.game
  - for (let i = 0; i < 9; i++)
    - const x = i % 3
    - const y = Math.floor(i / 3)
    input(type='checkbox' id=`x-${i}`)
    svg.x(style=`--x: ${x}; --y: ${y}` viewBox="0 0 100 100")
      path(d="M 80 20 L 20 80" stroke="black" stroke-width="10" stroke-linecap="round")
      path(d="M 20 20 L 80 80" stroke="black" stroke-width="10" stroke-linecap="round")
    input(type='checkbox' id=`o-${i}`)
    svg.o(style=`--x: ${x}; --y: ${y}` viewBox="0 0 100 100")
      circle(r="30" cx="50" cy="50" stroke-width="10" stroke-linecap="round" stroke="black" fill="none")
  .board
    - for (let l = 0; l < 4; l++)
      - const rotate = l % 2
      - const shift = 2 % (l + 1) ? 1 : -1
      svg.board__line(viewBox="0 0 10 300" style=`--rotate: ${rotate}; --shift: ${shift};`)
        path(d="M 5 5 L 5 295" stroke-width="10" stroke-linecap="round" stroke="black")
    - for (let i = 0; i < 9; i++)
      .board__cell
        label(for=`x-${i}`)
        label(for=`o-${i}`)
  .game__result.game__result--x X Wins!
  .game__result.game__result--o O Wins!
  .game__result.game__result--draw Draw...
  button(type='reset') Reset Board
!

CSS 

              
                *
  box-sizing border-box

:root
  --size 50vmin
  --cell-size calc(var(--size) / 3)

body
  min-height 100vh
  display grid
  place-items center
  margin 0
  overflow hidden

label
  position absolute
  height 100%
  width 100%

label:nth-of-type(odd)
  color red

label:nth-of-type(even)
  color green

input
  position fixed
  left 100%

button
  position absolute
  top 125%


.game
  position relative

  &__result
    display none


.board
  height var(--size)
  width var(--size)
  display grid
  grid-template-columns repeat(3, 1fr)
  grid-template-rows repeat(3, 1fr)
  place-items center

  &__line
    position absolute
    height var(--size)
    width calc(var(--size) * 0.05)
    left 50%
    top 50%
    transform translate(-50%, -50%) rotate(calc(var(--rotate, 0) * -90deg)) translateX(calc(var(--shift, 0) * ((var(--size) / 3) * 0.5)))

  &__cell
    height var(--cell-size)
    position relative
    width var(--cell-size)

.o
.x
  display none
  position absolute
  height var(--cell-size)
  width var(--cell-size)
  left calc(var(--x) * var(--cell-size))
  top calc(var(--y) * var(--cell-size))
  z-index 2

:checked + *
  display block

// Game mechanism
:checked ~ .board .board__cell label:nth-of-type(odd)
:checked ~ :checked ~ .board .board__cell label:nth-of-type(even)
:checked ~ :checked ~ :checked ~ .board .board__cell label:nth-of-type(odd)
:checked ~ :checked ~ :checked ~ :checked ~ .board .board__cell label:nth-of-type(even)
:checked ~ :checked ~ :checked ~ :checked ~ :checked ~ .board .board__cell label:nth-of-type(odd)
:checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ .board .board__cell label:nth-of-type(even)
:checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ .board .board__cell label:nth-of-type(odd)
:checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ .board .board__cell label:nth-of-type(even)
  display block

:checked ~ .board .board__cell label:nth-of-type(even)
:checked ~ :checked ~ .board .board__cell label:nth-of-type(odd)
:checked ~ :checked ~ :checked ~ .board .board__cell label:nth-of-type(even)
:checked ~ :checked ~ :checked ~ :checked ~ .board .board__cell label:nth-of-type(odd)
:checked ~ :checked ~ :checked ~ :checked ~ :checked ~ .board .board__cell label:nth-of-type(even)
:checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ .board .board__cell label:nth-of-type(odd)
:checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ .board .board__cell label:nth-of-type(even)
:checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ .board .board__cell label:nth-of-type(odd)
  display none

#x-0:checked ~ #x-1:checked ~ #x-2:checked ~ .game__result--x
#x-3:checked ~ #x-4:checked ~ #x-5:checked ~ .game__result--x
#x-6:checked ~ #x-7:checked ~ #x-8:checked ~ .game__result--x
#x-0:checked ~ #x-3:checked ~ #x-6:checked ~ .game__result--x
#x-1:checked ~ #x-4:checked ~ #x-7:checked ~ .game__result--x
#x-2:checked ~ #x-5:checked ~ #x-8:checked ~ .game__result--x
#x-0:checked ~ #x-4:checked ~ #x-8:checked ~ .game__result--x
#x-2:checked ~ #x-4:checked ~ #x-6:checked ~ .game__result--x
#o-0:checked ~ #o-1:checked ~ #o-2:checked ~ .game__result--o
#o-3:checked ~ #o-4:checked ~ #o-5:checked ~ .game__result--o
#o-6:checked ~ #o-7:checked ~ #o-8:checked ~ .game__result--o
#o-0:checked ~ #o-3:checked ~ #o-6:checked ~ .game__result--o
#o-1:checked ~ #o-4:checked ~ #o-7:checked ~ .game__result--o
#o-2:checked ~ #o-5:checked ~ #o-8:checked ~ .game__result--o
#o-0:checked ~ #o-4:checked ~ #o-8:checked ~ .game__result--o
#o-2:checked ~ #o-4:checked ~ #o-6:checked ~ .game__result--o
  display block

  ~ .game__result--draw
    display none

:checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked ~ :checked
  ~ .game__result--draw
    display block
!

JS
!
999px

Console