styles.less

* {
  box-sizing: border-box;
}

@font-face {
  /* http://www.dafont.com/ds-digital.font */
  font-family: 'DS-Digital';
  src: url(DS-DIGII.TTF);
}

body {
  background: black;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  width: 100vw;
  height: 100vh;
  font-family: sans-serif;
}

.calc-container {
  display: flex;
  flex-direction: column;
  padding: 10px;
  border-radius: 17px;
  background: #434343;
  width: 60%;
  max-width: 1000px;
  height: 80%;
  opacity: 0.93;

  .readout {
    position: relative;
    width: 100%;
    height: 15vmin;
    background: darkkhaki;
    border-radius: 10px;
    font-family: 'DS-Digital', monospace, sans-serif;
    display: flex;
    justify-content: flex-end;
    align-items: center;
    padding: 0 10px;
    font-size: 8vmin;
    font-weight: bold;
    overflow: hidden;
  }

  .plain-readout {
    display: flex;
    align-items: center;
    justify-content: flex-end;
    font-size: 3vmin;
    font-weight: 100;
    height: 8vmin;
    border-radius: 10px;
    margin-top: 10px;
    padding-right: 10px;
    background: #7e7a47;
  }

  .buttons {
    display: flex;
    flex-basis: 100%;
    font-size: 5vmin;
    padding: 5px;
    margin-top: 10px;
    border: 1px solid gray;
    border-radius: 10px;

    .button {
      cursor: pointer;
      border: 1px solid transparent;

      &:hover {
        background: white!important;
      }

      &.active {
        background: black!important;
        color: white;
      }
    }

    .number-pad {
      display: flex;
      flex-direction: column;
      flex-basis: 75%;

      .row {
        display: flex;
        flex-grow: 1;

        .pad {
          display: flex;
          flex-basis: 33.33333%;
          padding: 5px;

          &#zero {
            flex-basis: 66.66667%;
          }

          .button {
            display: flex;
            flex-grow: 1;
            justify-content: center;
            align-items: center;
            border-radius: 5px;
            user-select: none;
            background: rgb(143,225,143);

            &#colon {
              background: aquamarine;
            }
          }
        }
      }
    }

    .operators {
      display: flex;
      flex-direction: column;
      flex-basis: 25%;

      .operator {
        flex-grow: 1;
        display: flex;
        align-items: center;
        justify-content: center;
        cursor: pointer;
        border-radius: 5px;
        margin: 5px;
        user-select: none;

        &#clear,
        &#delete {
          background: rgba(0,255,255,0.85);
        }

        &#add,
        &#subtract {
          background: yellow;
        }

        &#equals {
          background: tomato;
        }
      }
    }
  }
}

// Random numbers for background.

.bg-overlay {
  width: 100%;
  height: 100%;
  position: absolute;
  top: 0;
  left: 0;
  z-index: -1;

  &::after {
    content: '';
    position: absolute;
    width: 100%;
    height: 100%;
    /* http://compresspng.com/ */
    background: url('grunge.png') no-repeat center center fixed;
    background-size: cover;
  }
}

.randoms {
  overflow: hidden;
  font-family: monospace;
  font-weight: bold;

  .random {
    position: absolute;
    text-shadow: 0 0 25px white;
  }
}


// Tablet breakpoint.
@media screen and (min-width: 768px) and (max-width: 1024px) {
  .calc-container {
    width: 80%;
    height: 80%;

    .readout {
      height: 15vh;
      font-size: 10vh;

      &::before {
        padding-top: 0.4vh;
      }
    }

    .plain-readout {
      height: 10vh;
      font-size: 4vh;
    }

    .buttons {
      padding: 3px;

      .button {
        font-size: 5vh;
      }
    }
  }
}

// Mobile breakpoint.
@media screen and (max-width: 767px) {
  .calc-container {
    width: 100vw;
    height: 100vh;
    border-radius: 0;

    .readout {
      height: 15vh;
      font-size: 10vh;

      &::before {
        padding-top: 0.8vh;
      }
    }

    .plain-readout {
      height: 10vh;
      font-size: 4vh;
    }

    .buttons {
      padding: 3px;

      .button {
        font-size: 6vh;
        margin: 3px;
      }
    }
  }
}