Code Playground

@charset "UTF-8";
@import url(https://fonts.googleapis.com/css?family=Nunito+Sans:300,400,600,700,800);
*,
:after,
:before {
  box-sizing: border-box;
  padding: 0;
  margin: 0;
}
@import url('https://fonts.googleapis.com/css2?family=Aboreto&display=swap');

@mixin flexCenter {
  display: flex;
  justify-content: center;
  align-items: center;
}

* {
  box-sizing: border-box;
}
html {
  font-size: 100vmax / 1600 * 100;
  @media (max-width: 992px) {
    font-size: 60px;
  }
}
body {
  min-height: 100vh;
  padding: 0.5rem;
  
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
  
  color: #222;
  background-color: #eee; // ✨ MUST ADD BG COLOR
  
  font-size: 0.24rem;
  font-family: 'Aboreto', sans-serif;
}

.card {
  width: 5rem;
  height: 1.8rem;
  padding: 0.3rem 0.5rem;
  
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.2rem;

line-height: 1.5;
  border: 1px solid;
  border-radius: 0.3rem;
  box-shadow: 3px 3px 0 3px #222;
  cursor: crosshair;
  overflow: hidden;
}

.arrow-btn {
  flex-shrink: 0;
  width: 0.7rem;
  height: 0.7rem;
  
  @include flexCenter;
  color: #eee;
  background-color: #222;
  border-radius: 50%;
  cursor: pointer;
  
  &:before {
    content: '\2192';
  }
}

input[type='checkbox'] {
  display: none;
  &:checked {
    ~ .dark-mode-mask {
      transform: scale(50);
    }
    ~ .toggle-btn {
      background-color: #fff;
    }
  }
}

// for dark mode
.dark-mode-mask, 
.toggle-btn {
  position: fixed;
  bottom: 0.3rem;
  right: 0.3rem;
  width: 1rem;
  height: 1rem;
  border-radius: 50%;
}

.toggle-btn {
  @include flexCenter;
  font-size: 0.8em;
  color: orange;
  background-color: #222;
  
  cursor: pointer;
  z-index: 1;
  transition: all 0.3s;
  will-change: background-color;
  // pulse effect
  &:before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 100%;
    height: 100%;
    
    background-color: inhrit;
    border-radius: inherit;
    animation: pulse 1.2s infinite linear;
    pointer-events: none;
  }
}

.dark-mode-mask {
  pointer-events: none;
  
  // ✨ trick here
  background-color: #fff;
  mix-blend-mode: difference;
  transition: all 0.5s ease;
  
  will-change: transform;
}

@keyframes pulse {
  0% {
    box-shadow: 0 0 0 0 #222a;
  }
  40% {
    box-shadow: 0 0 0 0.1rem #2222;
    opacity: 0.7;
  }
  80% {
    box-shadow: 0 0 0 0.15rem #2222;
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}

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