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CSS

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HTML 

              
                .stars
  each _ in Array(80)
    .star

.center
  .circle.circle--outer
  .circle.circle--inner
    .four.four--1 4
    .four.four--2 4
        
    .circle.oh
      .astronaut
        .astronaut-backpack
        .astronaut-head
        .astronaut-antena.antena--left
          .ear-down
          .ear-up
          .antena
          .antena-tip
          
        .astronaut-antena.antena--right
          .ear-down
          .ear-up
          .antena
          .antena-tip
          
        .astronaut-helmet
          .astronaut-glass
          .glow.glow--1
          .glow.glow--2
        
        .astronaut-body
        
      svg.astronaut-wire(viewBox="-9 -9 259 823" width="259" height="823")
        path(d="M241 0c-24 54-30 113-78 148S63 159 27 215c-35 55 32 102 73 141s103 94 98 166c-6 97-169 66-192 157-10 43-8 84 9 126" fill="none" stroke-width="6" stroke="#FFF")
      
      .circle.planet
        .craters
          .crater.crater--1
          .crater.crater--2
          .crater.crater--3
          .crater.crater--4
          .crater.crater--5
          .crater.crater--6
    
      .astronaut-hands
        .astronaut-hand.hand--left
          svg(width="35" height="75")
            path(d="M30.23 17.209c-7.925 5.118-11.657 12.786-11.226 22.975-7.113.934-12.948 4.345-18.44 5.117C-1.951 26.539 3.92 9.346 18.635 1.369 30.66-4.39 39.53 9.398 30.23 17.209z" fill="#D2D2D2")
            g(fill="none" stroke="#999" stroke-linecap="round")
              path(d="M11.78 6.977c7.983.129 13.547 3.968 16.308 11.111M4.67 17.161c7.307-.379 13.1 1.924 17.93 6.94")
              path(d="M.816 31.334c6.439-2.441 12.295-1.746 18.149 2.488" stroke-linejoin="round")
            g(fill="#fff")
              path(d="M7.721 37.171c5.875-1.994 12.264 1.156 14.258 7.031l1.218 3.588c1.995 5.875-1.156 12.264-7.03 14.258-5.875 1.995-12.264-1.156-14.259-7.031L.69 51.429c-1.994-5.875 1.156-12.263 7.031-14.258z")
              path(d="M7.829 38.159c5.794-1.967 12.094 1.14 14.061 6.934l5.044 14.855c1.967 5.794-1.14 12.095-6.934 14.062-5.794 1.967-12.095-1.14-14.062-6.934L.895 52.221c-1.967-5.794 1.14-12.095 6.934-14.062z")
              path(d="M16.863 39.472l12.879 7.384a3.876 3.876 0 0 1 1.433 5.287 3.875 3.875 0 0 1-5.286 1.433l-12.878-7.384a3.874 3.874 0 0 1-1.434-5.286 3.874 3.874 0 0 1 5.286-1.434z")

        .astronaut-hand.hand--right
          svg(width="35" height="75")
            path(d="M30.23 17.209c-7.925 5.118-11.657 12.786-11.226 22.975-7.113.934-12.948 4.345-18.44 5.117C-1.951 26.539 3.92 9.346 18.635 1.369 30.66-4.39 39.53 9.398 30.23 17.209z" fill="#D2D2D2")
            g(fill="none" stroke="#999" stroke-linecap="round")
              path(d="M11.78 6.977c7.983.129 13.547 3.968 16.308 11.111M4.67 17.161c7.307-.379 13.1 1.924 17.93 6.94")
              path(d="M.816 31.334c6.439-2.441 12.295-1.746 18.149 2.488" stroke-linejoin="round")
            g(fill="#fff")
              path(d="M7.721 37.171c5.875-1.994 12.264 1.156 14.258 7.031l1.218 3.588c1.995 5.875-1.156 12.264-7.03 14.258-5.875 1.995-12.264-1.156-14.259-7.031L.69 51.429c-1.994-5.875 1.156-12.263 7.031-14.258z")
              path(d="M7.829 38.159c5.794-1.967 12.094 1.14 14.061 6.934l5.044 14.855c1.967 5.794-1.14 12.095-6.934 14.062-5.794 1.967-12.095-1.14-14.062-6.934L.895 52.221c-1.967-5.794 1.14-12.095 6.934-14.062z")
              path(d="M16.863 39.472l12.879 7.384a3.876 3.876 0 0 1 1.433 5.287 3.875 3.875 0 0 1-5.286 1.433l-12.878-7.384a3.874 3.874 0 0 1-1.434-5.286 3.874 3.874 0 0 1 5.286-1.434z")

    .button GO HOME

  .sorry Oops! Sorry, page not found.



a(href='https://dribbble.com/shots/4571035-Error-404' class='inspiration' target='_blank' rel='noopener') inspiration
!

CSS 

              
                
random(a, b)
  return math(math(0, 'random')*(b - a + 1) + a, 'floor')  

@keyframes blink
  0%
  100%
    transform: scale(1)
    opacity: 1
  50%
    transform: scale(0.4)
    opacity: 0.5

@keyframes floating
  0%
  100%
    transform: translate(random(-3, 3)px, random(-3, 3)px) rotate(random(-2, 2)deg)
  20%
    transform: translate(random(-3, 3)px, random(-3, 3)px) rotate(random(-2, 2)deg)
  40%
    transform: translate(random(-3, 3)px, random(-3, 3)px) rotate(random(-2, 2)deg)
  60%
    transform: translate(random(-3, 3)px, random(-3, 3)px) rotate(random(-2, 2)deg)
  80%
    transform: translate(random(-3, 3)px, random(-3, 3)px) rotate(random(-2, 2)deg)

*
  box-sizing: border-box
  
body
  width: 100vw
  height: 100vh
  overflow: hidden
  font-size: 12px
  background-image: linear-gradient(to right bottom, #a9347e, #4b32a7)
  font-family: 'Open Sans', sans-serif
  letter-spacing: 0.2px
  color: white

.inspiration
  position: fixed
  bottom: 0
  right: 0
  padding: 10px
  text-align: center
  text-decoration: none
  font-family: 'Gill Sans', sans-serif
  font-size: 14px
  color: #ff487f

.center
  position: relative
  top: 50%
  left: 50%
  transform: translate(-50%, -50%)
  transition: transform 0.5s
  z-index: 1
  
  @media screen and (max-height: 600px)
    transform: translate(-50%, -50%) scale(0.75)
  @media screen and (max-width: 400px)
    transform: translate(-50%, -50%) scale(0.6)

.star
  position: absolute
  z-index: 1

for i in (1..80)
  size = random(1, 4)px
  
  .star:nth-child({i})
    top: random(0, 99)vh
    left: random(0, 99)vw
    
    &:before
    &:after
      position: absolute
      content: ''
      background-color: white
      border-radius: 10px
      animation: blink 1.5s infinite
      animation-delay: i * -1s
    
    &:before
      top: (size/2)
      left: -(size/2)
      width: 3 * size
      height: size
    &:after
      top: -(size/2)
      left: (size/2)
      width: size
      height: 3 * size
    
.circle
  position: absolute
  top: 50%
  left: 50%
  transform: translate(-50%, -50%)
  border-radius: 50%

.circle--outer
  width: 550px
  height: 550px
  background-image: linear-gradient(to right bottom, #802b89, #5631a1)
  box-shadow: 0px 0px 20px -8px black

.circle--inner
  width: 355px
  height: 355px
  background-image: linear-gradient(to right bottom, #75278b, #5530a2)
  box-shadow: 0px 0px 20px -8px black

.four
  position: absolute
  font-size: 150px
  font-weight: 900
  text-shadow: 0px 2px 10px rgba(0, 0, 0, 0.5)
  user-select: none
  
.four--1
  top: 100px
  left: 30px
  z-index: 1
.four--2
  top: 100px
  left: 230px
  z-index: 3

.astronaut
  position: absolute
  top: -115px
  left: -30px
  transform: rotate(17deg)
  
  .astronaut-backpack
    width: 100px
    height: 100px
    background-color: #e3e3e3
    border-radius: 10px
 
  .antena--left
    left: 10px
  .antena--right
    right: 10px
    
  .astronaut-antena
    position: absolute
    top: -7px
    
    .ear-down
      position: absolute
      bottom: -5px
      width: 15px
      height: 20px
      border-radius: 5px
      background-color: #afafaf
      z-index: 1
      
    .ear-up
      position: relative
      width: 15px
      height: 20px
      border-radius: 5px
      background-color: #c3c3c3
      z-index: 2
      
    .antena
      position: absolute
      top: -29px
      width: 2px
      height: 30px
      border-radius: 5px
      background-color: #c3c3c3

    .antena-tip
      position: absolute
      top: -33px
      width: 6px
      height: 6px
      border-radius: 50%
      background-color: #c3c3c3

  .antena--left .antena
    left: 5px
  .antena--right .antena
    right: 5px
  .antena--left .antena-tip
    left: 3px
  .antena--right .antena-tip
    right: 3px
      
  .astronaut-helmet
    position: absolute
    top: -30px
    left: 50%
    width: 66px
    height: 66px
    border-radius: 50%
    background-color: white
    box-shadow: 0px 5px 1px -3px gray
    transform: translateX(-50%)
    z-index: 3
    overflow: hidden
    
  .astronaut-glass
    position: absolute
    top: 13px
    left: 5px
    width: 56px
    height: 56px
    background: #00202e
    border-radius: 10px
  
  .glow
    position: absolute
    border-radius: 50%
    background-color: #334d57
    
  .glow--1
    top: 25px
    left: 15px
    width: 17px
    height: 17px
  
  .glow--2
    top: 44px
    left: 13px
    width: 7px
    height: 7px
  
  .astronaut-body
    position: absolute
    top: 30px
    left: 50%
    width: 50px
    height: 50px
    background-color: #c3c3c3
    transform: translateX(-50%)

.astronaut-wire
  position: absolute
  top: -40px
  left: -260px
    
.astronaut-hands
  position: absolute
  top: -89px
  left: -23px
  width: 100px
  transform: rotate(17deg)
  z-index: 3

  .astronaut-hand
    position: absolute

  .hand--left
    left: -3px
  .hand--right
    transform: scaleX(-1)
    right: -3px

.oh
  transition: all 0.1s linear
  animation: floating 4s linear infinite
  z-index: 2

.planet
  background-color: #ff4980
  box-shadow: inset -6px -10px 0px 1px #cc3b6b, 0px 2px 10px rgba(0, 0, 0, 0.4)
  width: 155px
  height: 155px
  
.craters
  .crater
    position: absolute
    border-radius: 50%
    background-color: #c93667

  .crater--1
    width: 35px
    height: 35px
    top: 30px
    left: 25px
  .crater--2
    width: 23px
    height: 23px
    top: 20px
    left: 93px
  .crater--3
    width: 17px
    height: 17px
    top: 77px
    left: 17px
  .crater--4
    width: 10px
    height: 10px
    top: 90px
    left: 80px
  .crater--5
    width: 25px
    height: 25px
    top: 115px
    left: 50px
  .crater--6
    width: 13px
    height: 13px
    top: 118px
    left: 105px

.button
  position: absolute
  bottom: 30px
  left: 50%
  transform: translateX(-50%)
  padding: 8px 12px
  border: 1px solid white
  border-radius: 3px
  cursor: pointer
  z-index: 999
  
  &:active
    transform: translateX(-50%) scale(0.95)

.sorry
  position: absolute
  top: 210px
  left: 50%
  transform: translateX(-50%)
  font-size: 15px
!

JS 

              
                /*
  Inspired by: "Error, 404"
  By: Sujeet Mishra
  Link: https://dribbble.com/shots/4571035-Error-404
*/

let oh = document.querySelector('.circle.oh')

document.addEventListener('mousemove', event => {
  let domainX = [0, document.body.clientWidth],
      domainY = [0, document.body.clientHeight],
      range = [-10, 10]
  
  let translate = {
    x: range[0] + (event.clientX - domainX[0]) * (range[1] - range[0])/(domainX[1] - domainX[0]),
    y: range[0] + (event.clientY - domainY[0]) * (range[1] - range[0])/(domainY[1] - domainY[0])
  }
  
  oh.style.animation = 'none'
  oh.style.transform = `translate(${translate.x}px, ${translate.y}px)`
})

document.addEventListener('mouseleave', event => {
  oh.style.animation = 'floating 3s linear infinite'
})
!
999px

Console