style.scss

html {
  box-sizing: border-box;
  font-size: 16px;
  font-family: Inter, sans-serif;
}

body {
  font-size: 16px;
}

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

body, h1, h2, h3, h4, h5, h6, p, ol, ul {
  margin: 0;
  padding: 0;
  font-weight: normal;
}

ol, ul {
  list-style: none;
}

img {
  max-width: 100%;
  height: auto;
}

input, button, select {
  font-family: Inter, sans-serif;
}

@font-face {
  font-family: 'Inter';
  font-weight: 100 900;
  font-display: swap;
  font-style: normal;
  font-named-instance: 'Regular';
  src: url("fonts/Inter-roman.var.woff2") format("woff2");
}

@font-face {
  font-family: 'Inter';
  font-weight: 100 900;
  font-display: swap;
  font-style: italic;
  font-named-instance: 'Italic';
  src: url("fonts/Inter-italic.var.woff2") format("woff2");
}

$grey: #ccc;
$border-grey: #eee;
$light: #f6f6f6;
$red: #f74c00;
$light-red: #fffafa;

html, body {
  height: 100%;
  max-height: 100vh;
}

header {
  height: 4rem;
  background: $light-red;
  display: flex;
  justify-content: space-between;
  align-items: center;

  h1 {
    line-height: 4rem;
    padding-left: 6.5rem;
    background: url('img/mailcrab.svg') no-repeat center left 1rem;
    background-size: 5rem;
    font-weight: 300;
    font-size: 2.5rem;

    span {
      color: $red;
      font-weight: 400;
    }
  }

  button {
    margin-right: 1rem;
    padding: 0 1rem 0 1.9rem;
    border: 1px solid $border-grey;
    cursor: pointer;
    border-radius: 0;
    font-weight: 400;
    font-size: 0.9rem;
    height: 2.5rem;
    line-height: 2rem;
    background: white url('img/trash.svg') no-repeat top 0.6rem left 0.75rem;
    background-size: 14px;

    span {
      font-size: 0.8rem;
      margin-left: 0.25rem;
      font-weight: 500;
    }

    &:hover {
      border-color: $red;
    }
  }
}

.main {
  height: calc(100vh - 4rem);
  display: flex;
  flex: 1;
}

.empty {
  margin: 4rem 0;
  text-align: center;
  font-size: 3rem;
  font-weight: 200;
  color: $grey;
}

@keyframes slide-down {
  from {
    padding: 0 0.75rem 0 3.5rem;
    max-height: 0;
  }
  to {
    padding: 0.75rem 0.75rem 0.75rem 3.5rem;
    max-height: 5rem;
  }
}

.list {
  border-right: 1px solid $border-grey;
  width: 30%;
  height: 100%;
  min-width: 40rem;
  max-width: 50rem;
  overflow-y: auto;

  ul {
    display: flex;
    flex-direction: column-reverse;
  }

  li {
    padding: 0.75rem 0.75rem 0.75rem 3.5rem;
    border-bottom: 1px solid $border-grey;
    line-height: 1.6;
    cursor: pointer;
    transition: all 150ms ease-in;
    animation: slide-down 300ms ease-in;
    overflow: hidden;
    font-size: 0.9rem;
    background: white url('img/envelope.svg') no-repeat center left 0.75rem;
    background-size: 2rem;

    &:last-child {
      border-top: 1px solid $border-grey;
    }

    &:hover, &.selected {
      background-color: $light-red;
    }

    &.opened {
      opacity: 0.5;
      background-image: url('img/envelope-open.svg');
    }

    &.selected {
      color: black !important;
      font-weight: 500;
      background-image: url('img/envelope-open-text.svg');
    }

    .head {
      display: flex;
      justify-content: space-between;

      .name {
        font-weight: 500;
      }

      .name + .email {
        margin-left: 0.5rem;
        color: rgba(black, 0.3);
        
        &::before {
          content: '<';
        }

        &::after {
          content: '>';
        }
      }
    }

    .preview {
      display: flex;
      justify-content: space-between;

      .subject {
        color: rgba(black, 0.9);
        display: block;
      }

      .size {
        margin-left: 0.5rem;
        color: rgba(black, 0.3);
      }
    }

    &.attachments {
      .subject::before {
        content: ' ';
        display: inline-block;
        margin-right: 0.2rem;
        width: 0.9rem;
        height: 0.9rem;
        background: url('img/paperclip.svg') no-repeat center left;
      }
    }
  }
}

.view {
  background-color: $light;
  padding: 1rem;
  flex: 1;
  overflow-x: hidden;
  border-top: 1px solid $border-grey;

  .view-inner {
    background-color: white;
    height: 100%;
    display: flex;
    flex-direction: column;

    ul {
      display: block;
      background-color: $light;
      display: flex;

      li {
        button {
          font-size: 1rem;
          padding: 0.75rem 1.5rem;
          margin-right: 0.3rem;
          cursor: pointer;
          border: none;
          background-color: darken($light, 5%);
          transition: all 150ms ease-in;

          &:hover, &.active {
            background: white;
          }
        }

        &.delete {
          margin-left: auto;

          button {
            margin-right: 0;
            margin-bottom: 0.25rem;
            padding: 0.5rem 1.5rem 0.5rem 2rem;
            background: white url('img/trash.svg') no-repeat center left 1rem;
            background-size: 12px;
            border: 1px solid $grey;

            &:hover {
              border: 1px solid $red;
            }
          }
        }
      }
    }

    .tab-content {
      height: 100%;
      display: flex;
      flex-direction: column;
      padding: 1rem;
      overflow-x: hidden;
      font-size: 0.9rem;

      table {
        border-collapse: collapse;

        th {
          font-weight: 500;
          text-align: left;
          width: 10rem;
        }

        td, th {
          padding: 0.5rem;
          border-bottom: 1px solid lighten($grey, 10%);
        }

        .name {
          font-weight: 500;
        }
  
        .name + .email {
          color: rgba(black, 0.8);
          
          &::before {
            content: ' <';
          }
  
          &::after {
            content: '>';
          }
        }
      }

      .attachments {
        a {
          display: inline-block;
          padding: 0.5rem 0.5rem 0.5rem 2rem;
          margin: 0.75rem 0.5rem 0 0;
          font-size: 0.9rem;
          border: 1px solid $grey;
          text-decoration: none;
          color: black;
          transition: all 150ms ease-in;
          background: white url('img/file.svg') no-repeat center left 0.5rem;
          background-size: 1rem;

          &.application-pdf {
            background-image: url('img/file-pdf.svg') 
          }

          .size {
            margin-left: 0.5rem;
            font-size: 0.8rem;
            color: rgba(black, 0.7);
          }

          &:hover {
            background-color: $light-red;
          }
        }
      }

      pre {
        overflow-x: hidden;
        white-space: pre-wrap;
        word-wrap: break-word;
        margin: 0;
        padding: 0;
      }

      .body {
        width: 100%;
        flex: 1;
        padding: 0;
        margin-top: 0.75rem;

        pre {
          font-family: Inter, sans-serif;
          line-height: 1.4;
        }

        iframe, pre {
          border: 1px solid $border-grey;
          width: 100%;
          height: 100%;
          padding: 0.5rem;
        }
      }
    }
  }
}