node_modules/gitbook-plugin-theme-cuav/src/scss/gitbook/_header.scss

// Copyright 2017 CUAV.
// 
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// 
//    http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// 新增 _header.scss

.book-header {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  background: rgb(250, 250, 250);
  @include transition(left 250ms ease);
}

.book {
  &.with-summary {
    .book-header {
      left: $sidebar-width;
      @include transform(none!important);

      @media (max-width: $sidebar-breakpoint) {
        @include body-position;
      }
    }
  }

  &.without-animation {
    .book-header {
      @include transition(none!important);
    }
  }
}