<div class="fire">
   <div class="flames">
      <div class="flame"></div>
      <div class="flame"></div>
      <div class="flame"></div>
      <div class="flame"></div>
   </div>
   <div class="logs"></div>
</div>

$black:#111217;
$brownl:#70392F;
$brownd:#612E25;
$yellow:#FFDC01;
$orange:#FDAC01;
$red:#F73B01;
$animationtime:1.5s;

body {
   background-color:$black;
   .fire {
      position: absolute;
      top:50%;
      left:50%;
      transform:translate(-50%,-25%);
      height:20vw;
      width:20vw;
      //background-color:$red;
      .flames {
         position: absolute;
         bottom:40%;
         left:50%;
         width:60%;
         height:60%;
         //background-color:$red;
         transform:translateX(-50%)rotate(45deg);
         .flame {
            position: absolute;
            right:0%;
            bottom:0%;
            width:0%;
            height:0%;
            background-color:$yellow;
            border-radius:1vw;
            &:nth-child(2n + 1) {
               animation: flameodd $animationtime ease-in infinite;
            }
            &:nth-child(2n) {
               animation: flameeven $animationtime ease-in infinite;
            }
            &:nth-child(1) {
               animation-delay:0s;
            }
            &:nth-child(2) {
               animation-delay:$animationtime/4;
            }
            &:nth-child(3) {
               animation-delay:$animationtime/4 * 2;
            }
            &:nth-child(4) {
               animation-delay:$animationtime/4 * 3;
            }
         }
      }
      .logs {
         position: absolute;
         bottom:25%;
         left:50%;
         transform:translateX(-50%);
         width:100%;
         height:15%;
         &:before, &:after {
            position: absolute;
            content: '';
            top:50%;
            left:50%;
            transform:translate(-50%,-50%) rotate(20deg);
            height:100%;
            width:100%;
            border-radius:1vw;
            background-color:$brownl;
         }
         &:before {
            transform:translate(-50%,-50%) rotate(-20deg);
            background-color:$brownd;
         }
      }
   }
}

@keyframes flameodd {
   0%, 100% {
      width:0%;
      height:0%;
   }
   25% {
      width:100%;
      height:100%;
   }
   0% {
      background-color:$yellow;
      z-index:1000000;
   }
   40% {
      background-color:$orange;
      z-index:1000000;
   }
   100% {
      background-color:$red;
      z-index:-10;
   }
   0% {
      right:0%;
      bottom:0%;
   }
   25% {
      right:1%;
      bottom:2%;
   }
   100% {
      right:150%;
      bottom:170%;
   }
}

@keyframes flameeven {
   0%, 100% {
      width:0%;
      height:0%;
   }
   25% {
      width:100%;
      height:100%;
   }
   0% {
      background-color:$yellow;
      z-index:1000000;
   }
   40% {
      background-color:$orange;
      z-index:1000000;
   }
   100% {
      background-color:$red;
      z-index:-10;
   }
   0% {
      right:0%;
      bottom:0%;
   }
   25% {
      right:2%;
      bottom:1%;
   }
   100% {
      right:170%;
      bottom:150%;
   }
}