mkdocs-material/src/assets/stylesheets/layout/_header.scss

/*
 * Copyright (c) 2016 Martin Donath <martin.donath@squidfunk.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

/* ----------------------------------------------------------------------------
 * Header
 * ------------------------------------------------------------------------- */

/*
 * Application header (stays always on top)
 */
.md-header {
  @include drop-shadow(1);

  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 5.6rem;
  z-index: 1;
  background: $md-color-primary;
  color: $md-color-white;

  /*
   * Navigation within header
   */
  &-nav {
    padding: 0.4rem;

    /*
     * Icon
     */
    &__icon {
      display: inline-block;
      font-size: 2.4rem;
      padding: 0.8rem;
      margin: 0.4rem;
      cursor: pointer;
      border-radius: 100%;
      transition: background .25s;

      /*
       * Pushed/clicked icon
       */
      &:active {
        background: $md-color-white--lightest;
      }

      /* [tablet portrait +]: Hide the search icon */
      @include break-from-device(tablet landscape) {

        /*
         * Search icon
         */
        &.md-icon--search {
          display: none;
        }
      }
    }

    /*
     * Title
     */
    &__title {
      padding: 0 2.0rem;
      font-size: 1.8rem;
      line-height: 4.8rem;
    }
  }

  /*
   * Search bar within header - the right aligment removes jitter
   */
  &-search {
    position: relative;
    margin: 0.6rem 0.4rem 0.6rem 0;
    text-align: right;

    /*
     * Icon
     */
    &__icon {
      position: absolute;
      top: 0.6rem;
      left: 1.2rem;
      font-size: 2.4rem;
      transition: color .25s;
      cursor: pointer;
    }

    /*
     * Search field
     */
    &__input {
      display: inline-block;
      width: 23.0rem;
      height: 3.6rem;
      padding-left: 4.4rem;
      padding-right: 0.8rem;
      font-size: ms(0);
      background: $md-color-white--lightest;
      color: $md-color-white;
      border-radius: px2rem(2px);
      transition: color            .25s,
                  background-color .25s,
                  width            .25s cubic-bezier(0.1, 0.7, 0.1, 1);

      /*
       * Placeholder color
       */
      &::placeholder {
        color: $md-color-white;
        transition: color .25s;
      }

      /*
       * Active search field
       */
      &:focus {
        background: $md-color-white;
        color: $md-color-black;
        width: 40rem;

        /*
         * Placeholder and icon color in active state
         */
        + .md-header-search__icon,
        &::placeholder {
          color: $md-color-black--light;
        }
      }
    }
  }
}