style.css

*,
*:after,
*:before {
  box-sizing: border-box;
}

body {
  padding: 0;
  margin: 0;
}

.container {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100vh;
  overflow: hidden;
}



.container-title {
  width: 600px;
  height: 450px;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  position: absolute;
  color: #b13f2b;
  line-height: 1;
  font-weight: 700;
  text-align: center;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  display: flex;
}

.title>* {
  display: inline-block;
  font-size: 200px;
}

.number {
  text-shadow: 20px 20px 20px rgba(0, 0, 0, 0.2);
  padding: 0 0.2em;
  font-family: "Russo One", sans-serif;
}

.subtitle {
  font-size: 25px;
  margin-top: 1.5em;
  font-family: "Lato", sans-serif;
  text-shadow: 4px 4px 4px rgba(0, 0, 0, 0.2);
}

button {
  font-size: 22px;
  margin-top: 1.5em;
  padding: 0.5em 1em;
  letter-spacing: 1px;
  font-family: "Lato", sans-serif;
  color: white;
  background-color: transparent;
  border: 0;
  cursor: pointer;
  z-index: 999;
  border: 2px solid white;
  border-radius: 5px;
  text-shadow: 4px 4px 4px rgba(0, 0, 0, 0.2);
  transition: opacity 0.2s ease;
}

button:hover {
  opacity: 0.7;
}

button:focus {
  outline: 0;
}

.moon {
  position: relative;
  border-radius: 50%;
  width: 160px;
  height: 160px;
  z-index: 2;
  background-color: #b13f2b;
  box-shadow: 0 0 10px #b13f2b, 0 0 20px #b13f2b, 0 0 30px #b13f2b, 0 0 40px #b13f2b, 0 0 70px #b13f2b, 0 0 80px #b13f2b, 0 0 100px #b13f2b;
  -webkit-animation: rotate 5s ease-in-out infinite;
  animation: rotate 5s ease-in-out infinite;
}

.moon .face {
  top: 60%;
  left: 47%;
  position: absolute;
}

.moon .face .mouth {
  border-top-left-radius: 50%;
  border-bottom-right-radius: 50%;
  border-top-right-radius: 50%;
  background-color: #fff;
  width: 25px;
  height: 25px;
  position: absolute;
  -webkit-animation: snore 5s ease-in-out infinite;
  animation: snore 5s ease-in-out infinite;
  transform: rotate(45deg);
  box-shadow: inset -4px -4px 4px rgba(0, 0, 0, 0.3);
}

.moon .face .eyes {
  position: absolute;
  top: -30px;
  left: -30px;
}

.moon .face .eyes .eye-left,
.moon .face .eyes .eye-right {
  border: 4px solid #fff;
  width: 30px;
  height: 15px;
  border-bottom-left-radius: 100px;
  border-bottom-right-radius: 100px;
  border-top: 0;
  position: absolute;
}

.moon .face .eyes .eye-left:before,
.moon .face .eyes .eye-left:after,
.moon .face .eyes .eye-right:before,
.moon .face .eyes .eye-right:after {
  content: "";
  position: absolute;
  border-radius: 50%;
  width: 4px;
  height: 4px;
  background-color: #fff;
  top: -2px;
  left: -4px;
}

.moon .face .eyes .eye-left:after,
.moon .face .eyes .eye-right:after {
  left: auto;
  right: -4px;
}

.moon .face .eyes .eye-right {
  left: 50px;
}

.container-bird {
  perspective: 2000px;
  width: 100%;
  height: 100%;
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
}

.bird {
  position: absolute;
  z-index: 1000;
  left: 50%;
  top: 50%;
  height: 40px;
  width: 50px;
  transform: translate3d(-100vw, 0, 0) rotateY(90deg);
  transform-style: preserve-3d;
}

.bird-container {
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transform: translate3d(50px, 30px, -300px);
}

.wing {
  position: absolute;
  left: 0;
  top: 0;
  right: 0;
  bottom: 0;
  border-radius: 3px;
  transform-style: preserve-3d;
  transform-origin: center bottom;
  z-index: 300;
}

.wing-left {
  background: linear-gradient(to bottom, #a58dc4 0%, #7979a8 100%);
  transform: translate3d(0, 0, 0) rotateX(-30deg);
  -webkit-animation: wingLeft 1.3s cubic-bezier(0.45, 0, 0.5, 0.95) infinite;
  animation: wingLeft 1.3s cubic-bezier(0.45, 0, 0.5, 0.95) infinite;
}

.wing-right {
  background: linear-gradient(to bottom, #d9d3e2 0%, #b8a5d1 100%);
  transform: translate3d(0, 0, 0) rotateX(-30deg);
  -webkit-animation: wingRight 1.3s cubic-bezier(0.45, 0, 0.5, 0.95) infinite;
  animation: wingRight 1.3s cubic-bezier(0.45, 0, 0.5, 0.95) infinite;
}

.wing-right-top,
.wing-left-top {
  border-right: 25px solid transparent;
  border-left: 25px solid transparent;
  top: -20px;
  width: 100%;
  position: absolute;
  transform-origin: 100% 100%;
}

.wing-right-top {
  border-bottom: 20px solid #b8a5d1;
  transform: translate3d(0, 0, 0) rotateX(60deg);
  -webkit-animation: wingRightTop 1.3s cubic-bezier(0.45, 0, 0.5, 0.95) infinite;
  animation: wingRightTop 1.3s cubic-bezier(0.45, 0, 0.5, 0.95) infinite;
}

.wing-left-top {
  border-bottom: 20px solid #7979a8;
  transform: translate3d(0, 0, 0) rotateX(-60deg);
  -webkit-animation: wingLeftTop 1.3s cubic-bezier(0.45, 0, 0.5, 0.95) infinite;
  animation: wingLeftTop 1.3s cubic-bezier(0.45, 0, 0.5, 0.95) infinite;
}

.bird-anim:nth-child(1) {
  -webkit-animation: bird1 30s linear infinite forwards;
  animation: bird1 30s linear infinite forwards;
}

.bird-anim:nth-child(2) {
  -webkit-animation: bird2 30s linear infinite forwards;
  animation: bird2 30s linear infinite forwards;
  -webkit-animation-delay: 3s;
  animation-delay: 3s;
  z-index: -1;
}

.bird-anim:nth-child(3) {
  -webkit-animation: bird3 30s linear infinite forwards;
  animation: bird3 30s linear infinite forwards;
  -webkit-animation-delay: 5s;
  animation-delay: 5s;
}

.bird-anim:nth-child(4) {
  -webkit-animation: bird4 30s linear infinite forwards;
  animation: bird4 30s linear infinite forwards;
  -webkit-animation-delay: 7s;
  animation-delay: 7s;
}

.bird-anim:nth-child(5) {
  -webkit-animation: bird5 30s linear infinite forwards;
  animation: bird5 30s linear infinite forwards;
  -webkit-animation-delay: 14s;
  animation-delay: 14s;
}

.bird-anim:nth-child(6) {
  -webkit-animation: bird6 30s linear infinite forwards;
  animation: bird6 30s linear infinite forwards;
  -webkit-animation-delay: 10s;
  animation-delay: 10s;
  z-index: -1;
}

@-webkit-keyframes rotate {

  0%,
  100% {
    transform: rotate(-8deg);
  }

  50% {
    transform: rotate(0deg);
  }
}

@keyframes rotate {

  0%,
  100% {
    transform: rotate(-8deg);
  }

  50% {
    transform: rotate(0deg);
  }
}

@-webkit-keyframes snore {

  0%,
  100% {
    transform: scale(1) rotate(30deg);
  }

  50% {
    transform: scale(0.5) rotate(30deg);
    border-bottom-left-radius: 50%;
  }
}

@keyframes snore {

  0%,
  100% {
    transform: scale(1) rotate(30deg);
  }

  50% {
    transform: scale(0.5) rotate(30deg);
    border-bottom-left-radius: 50%;
  }
}

@-webkit-keyframes twinkle {

  0%,
  100% {
    opacity: 0.7;
  }

  50% {
    opacity: 0.3;
  }
}

@keyframes twinkle {

  0%,
  100% {
    opacity: 0.7;
  }

  50% {
    opacity: 0.3;
  }
}

@-webkit-keyframes wingLeft {

  0%,
  100% {
    transform: translate3d(0, 0, 0) rotateX(-50deg);
  }

  50% {
    transform: translate3d(0, -20px, 0) rotateX(-130deg);
    background: linear-gradient(to bottom, #d9d3e2 0%, #b8a5d1 100%);
  }
}

@keyframes wingLeft {

  0%,
  100% {
    transform: translate3d(0, 0, 0) rotateX(-50deg);
  }

  50% {
    transform: translate3d(0, -20px, 0) rotateX(-130deg);
    background: linear-gradient(to bottom, #d9d3e2 0%, #b8a5d1 100%);
  }
}

@-webkit-keyframes wingLeftTop {

  0%,
  100% {
    transform: translate3d(0, 0, 0) rotateX(-10deg);
  }

  50% {
    transform: translate3d(0px, 0px, 0) rotateX(-40deg);
    border-bottom: 20px solid #b8a5d1;
  }
}

@keyframes wingLeftTop {

  0%,
  100% {
    transform: translate3d(0, 0, 0) rotateX(-10deg);
  }

  50% {
    transform: translate3d(0px, 0px, 0) rotateX(-40deg);
    border-bottom: 20px solid #b8a5d1;
  }
}

@-webkit-keyframes wingRight {

  0%,
  100% {
    transform: translate3d(0, 0, 0) rotateX(50deg);
  }

  50% {
    transform: translate3d(0, -20px, 0) rotateX(130deg);
    background: linear-gradient(to bottom, #a58dc4 0%, #7979a8 100%);
  }
}

@keyframes wingRight {

  0%,
  100% {
    transform: translate3d(0, 0, 0) rotateX(50deg);
  }

  50% {
    transform: translate3d(0, -20px, 0) rotateX(130deg);
    background: linear-gradient(to bottom, #a58dc4 0%, #7979a8 100%);
  }
}

@-webkit-keyframes wingRightTop {

  0%,
  100% {
    transform: translate3d(0, 0, 0) rotateX(10deg);
  }

  50% {
    transform: translate3d(0px, 0px, 0px) rotateX(40deg);
    border-bottom: 20px solid #7979a8;
  }
}

@keyframes wingRightTop {

  0%,
  100% {
    transform: translate3d(0, 0, 0) rotateX(10deg);
  }

  50% {
    transform: translate3d(0px, 0px, 0px) rotateX(40deg);
    border-bottom: 20px solid #7979a8;
  }
}

@-webkit-keyframes bird1 {
  0% {
    transform: translate3d(-120vw, -20px, -1000px) rotateY(-40deg) rotateX(0deg);
  }

  100% {
    transform: translate3d(100vw, -40vh, 1000px) rotateY(-40deg) rotateX(0deg);
  }
}

@keyframes bird1 {
  0% {
    transform: translate3d(-120vw, -20px, -1000px) rotateY(-40deg) rotateX(0deg);
  }

  100% {
    transform: translate3d(100vw, -40vh, 1000px) rotateY(-40deg) rotateX(0deg);
  }
}

@-webkit-keyframes bird2 {

  0%,
  15% {
    transform: translate3d(100vw, -300px, -1000px) rotateY(10deg) rotateX(0deg);
  }

  100% {
    transform: translate3d(-100vw, -20px, -1000px) rotateY(10deg) rotateX(0deg);
  }
}

@keyframes bird2 {

  0%,
  15% {
    transform: translate3d(100vw, -300px, -1000px) rotateY(10deg) rotateX(0deg);
  }

  100% {
    transform: translate3d(-100vw, -20px, -1000px) rotateY(10deg) rotateX(0deg);
  }
}

@-webkit-keyframes bird3 {
  0% {
    transform: translate3d(100vw, -50vh, 100px) rotateY(-5deg) rotateX(-20deg);
  }

  100% {
    transform: translate3d(-100vw, -10vh, 100px) rotateY(-5deg) rotateX(-20deg);
  }
}

@keyframes bird3 {
  0% {
    transform: translate3d(100vw, -50vh, 100px) rotateY(-5deg) rotateX(-20deg);
  }

  100% {
    transform: translate3d(-100vw, -10vh, 100px) rotateY(-5deg) rotateX(-20deg);
  }
}

@-webkit-keyframes bird4 {
  0% {
    transform: translate3d(100vw, 30vh, 200px) rotateY(-5deg) rotateX(10deg);
  }

  100% {
    transform: translate3d(-100vw, -30vh, 200px) rotateY(-5deg) rotateX(10deg);
  }
}

@keyframes bird4 {
  0% {
    transform: translate3d(100vw, 30vh, 200px) rotateY(-5deg) rotateX(10deg);
  }

  100% {
    transform: translate3d(-100vw, -30vh, 200px) rotateY(-5deg) rotateX(10deg);
  }
}

@-webkit-keyframes bird5 {

  0%,
  5% {
    transform: translate3d(100vw, 30vh, 400px) rotateY(-15deg) rotateX(-10deg);
  }

  100% {
    transform: translate3d(-100vw, 10vh, 400px) rotateY(-15deg) rotateX(-10deg);
  }
}

@keyframes bird5 {

  0%,
  5% {
    transform: translate3d(100vw, 30vh, 400px) rotateY(-15deg) rotateX(-10deg);
  }

  100% {
    transform: translate3d(-100vw, 10vh, 400px) rotateY(-15deg) rotateX(-10deg);
  }
}

@-webkit-keyframes bird6 {

  0%,
  10% {
    transform: translate3d(-100vw, 20vh, -500px) rotateY(15deg) rotateX(10deg);
  }

  100% {
    transform: translate3d(100vw, 40vh, -800px) rotateY(5deg) rotateX(10deg);
  }
}

@keyframes bird6 {

  0%,
  10% {
    transform: translate3d(-100vw, 20vh, -500px) rotateY(15deg) rotateX(10deg);
  }

  100% {
    transform: translate3d(100vw, 40vh, -800px) rotateY(5deg) rotateX(10deg);
  }
}

@media screen and (max-width: 580px) {
  .container-404 {
    width: 100%;
  }

  .number {
    font-size: 100px;
  }

  .subtitle {
    font-size: 20px;
    padding: 0 1em;
  }

  .moon {
    width: 100px;
    height: 100px;
  }

  .face {
    transform: scale(0.7);
  }
}

button {
  color: #b13f2b;
  border-color: #b13f2b;
}