styles-main.css

.icon {
  &::before {
    font-family: 'icomoon' !important;
    speak: none;
    font-style: normal;
    font-weight: normal;
    font-variant: normal;
    text-transform: none;
    font-size: 24px;
    vertical-align: middle;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    margin-right: 8px;
  }
}

styles.css

.header {
  display: flex;
  align-items: stretch;
  height: 64px;
  background-color: #fff;
  box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.07), 0 1px 0 0 rgba(0, 0, 0, 0.03);
}

.back {
  composes: icon from 'styles/main';
  display: inherit;
  align-self: center;
  width: 40px;
  height: 64px;
  line-height: 64px;
  text-decoration: none;
  text-align: center;
  border-right: #e0e0e0 solid 1px;

  &:hover {
    background-color: #e0e0e0;

    &::before {
      color: #000;
    }
  }

  &::before {
    margin-left: 8px;
    color: #e0e0e0;
    content: '\e900';
  }
}

.buttons {
  display: inherit;
  justify-content: flex-end;
  align-items: center;
  flex-grow: 1;
  background-color: #fff;
  padding-right: 32px;
}

.button {
  width: 215px;
  height: 30px;
  border-radius: 7px;
  background-color: #fff;
  box-shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.07);
  border: solid 1px rgba(0, 0, 0, 0.13);
  font-family: "Open Sans";
  font-size: 14px;
  color: #000;
  outline: none;
  cursor: pointer;

  &:hover {
    box-shadow: 0 12px 24px 0 rgba(0, 0, 0, 0.13);
  }
}

.connect {
  composes: button;
  margin-right: 16px;
}

.test {
  composes: button;
  background-color: #448af1;
  color: #fff;

  &:hover {
    background-color: #4e94fe;
  }
}