app.mcss

body {
  /* background: #222 */
}

App {
  position: fixed
  top: 0
  bottom: 0
  left: 0
  right: 0

  display: grid
  grid-template-columns: auto 1fr

  div.settings {
    padding: 1rem

    display: grid
    grid-gap: 2rem
    align-content: start

    div.Segment {
      background: #fff
      padding: 1rem

      border: 1px dashed #222
    }

    div.Colors {
      background: #fff
      padding: 1rem

      border: 1px dashed #222
    }
  }

  div.Preview {
  }
}