index.scss

@mixin flexcenter($direction) {
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: $direction;
}

$color2: rgb(215, 126, 126);

@mixin shadow {
  box-shadow: 4px 4px 10px rgba(0, 0, 0, 0.509),
    -4px -4px 10px rgba(255, 255, 255, 0.735);
}

@mixin insetShadow {
  box-shadow: inset 2px 2px 3px rgba(0, 0, 0, 0.495),
    inset -1px -1px 4px rgba(255, 255, 255, 0.523);
}

@mixin textShadow {
  text-shadow: 1px 1px 2px rgba(0, 0, 0, 0.392),
    -1px -1px 2px rgba(255, 255, 255, 0.434);
}

$bgcolor: rgb(223, 223, 223);

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  height: 100%;
}

body {
  height: 100%;
  background: $bgcolor;
  @include flexcenter(column);
}

#container {
  // @include flexcenter(column);
  @include shadow();
  width: 300px;
  height: 400px;
  // margin: 30px auto;
  background: lightblue;
  border-radius: 20px;
  font-family: sans-serif;
  padding: 20px;
  position: relative;

  h3 {
    text-align: center;
    color: $color2;
    font-weight: 500;
    // @include textShadow();
    margin: 30px 20px;
    font-size: 22px;
  }

  #input {
    background-color: $bgcolor;
    border: none;
    height: 30px;
    outline: none;
    text-align: center;
    color: rgb(77, 77, 77);
    border-radius: 20px;
    @include insetShadow();
    display: flex;
    margin: 30px auto;
    font-size: 20px;
  }
  #check {
    padding: 10px;
    width: 200px;
    border: 1px solid rgb(174, 96, 96);
    border-radius: 20px;
    background-color: $color2;
    color: whitesmoke;
    outline: none;
    @include shadow();
    @include textShadow();
    display: flex;
    justify-content: center;
    align-items: center;
    text-align: center;
    margin: 20px auto;
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);

    &:active {
      box-shadow: inset 1px 1px 2px rgba(0, 0, 0, 0.543);
    }
  }

  #check,
  #output {
    margin-top: 30px;
  }

  #output {
    color: rgb(77, 77, 77);
    text-align: center;
  }
}