metamask-extension/ui/app/css/itcss/components/newui-sections.scss

/*
  NewUI Container Elements
 */

.main-container {
  position: absolute;
  z-index: 18;
  box-shadow: 0 0 7px 0 rgba(0,0,0,0.08);
  font-family: DIN OT;
  display: flex;
  flex-wrap: wrap;
  align-items: stretch;
  overflow-y: scroll;
}

.sidebar {
  flex: 1 0 230px;
  background: rgb(250, 250, 250);
  z-index: 26;
  position: fixed;
  top: 35px;
  left: 0px;
  right: 0px;
  bottom: 0px;
  opacity: 1;
  visibility: visible;
  will-change: transform;
  overflow-y: auto;
  box-shadow: rgba(0, 0, 0, 0.15) 2px 2px 4px;
  width: 85%;
  height: 100%;
}

.sidebar-overlay {
  z-index: 25;
  position: fixed;
  top: 35px;
  left: 0px;
  right: 0px;
  bottom: 0px;
  opacity: 1;
  visibility: visible;
  background-color: rgba(0, 0, 0, 0.3);
}

@media screen and (min-width: 576px) {
  .lap-visible {
    display: flex;
  }

  .phone-visible {
    display: none;
  }

  .main-container {
    margin-top: 35px;
    width: 85%;
    height: 90vh;
  }

  button.btn-clear {
    width: 75px;
    height: 32px;
    font-size: .6em;
    background: white;
    border: 1px solid;
  }
}

@media screen and (min-width: 769px) {
  .main-container {
    margin-top: 35px;
    width: 80%;
    height: 82vh;
  }
}

@media screen and (min-width: 1281px) {
  .main-container {
    margin-top: 35px;
    width: 65%;
    height: 82vh;
  }
}

@media screen and (max-width: 575px) {
  .lap-visible {
    display: none;
  }

  .phone-visible {
    display: flex;
  }

  .main-container {
    margin-top: 35px;
    // position: relative;
    width: 100%;
    height: 100%;
  }

  button.btn-clear {
    width: 100px;
    height: 50px;
    font-size: .7em;
    background: red;
    border: 1px solid;
  }
}