/* study999-lesson-nav-v2
   课文顶部和底部统一为三个导航按钮。
*/

#app .study999-lesson-nav-section {
  box-sizing: border-box;
  width: 100%;
}

#app .study999-lesson-nav-row {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  align-items: stretch;
  gap: 10px;
  width: 100%;
  min-width: 0;
}

#app .study999-lesson-nav-btn {
  box-sizing: border-box;
  display: flex;
  flex-direction: row;
  align-items: center;
  justify-content: center;
  gap: 8px;

  width: 100%;
  min-width: 0;
  min-height: 48px;

  margin: 0;
  padding: 10px 8px;

  border: 1px solid transparent;
  border-radius: 11px;

  font: 650 15px/1.35 system-ui, "Microsoft YaHei", sans-serif;
  white-space: nowrap;
  text-align: center;
  cursor: pointer;
}

#app .study999-lesson-nav-btn svg {
  display: block;
  width: 20px;
  height: 20px;
  flex: 0 0 20px;
}

#app .study999-lesson-nav-btn span {
  min-width: 0;
}

/* 上一课：蓝色 */
#app .study999-lesson-nav-btn[data-lesson-nav="previous"] {
  color: #1d4ed8;
  background: #eff6ff;
  border-color: #bfdbfe;
}

/* 章节目录：绿色 */
#app .study999-lesson-nav-btn[data-lesson-nav="back"] {
  color: #047857;
  background: #ecfdf5;
  border-color: #a7f3d0;
}

/* 下一课：紫色 */
#app .study999-lesson-nav-btn[data-lesson-nav="next"] {
  color: #6d28d9;
  background: #f5f3ff;
  border-color: #ddd6fe;
}

#app .study999-lesson-nav-btn:not(:disabled):hover {
  filter: brightness(.96);
}

#app .study999-lesson-nav-btn:focus-visible {
  outline: 3px solid #93c5fd;
  outline-offset: 2px;
}

/* 第一课或最后一课：文字不变，只显示禁用状态。 */
#app .study999-lesson-nav-btn:disabled {
  color: #94a3b8;
  background: #f1f5f9;
  border-color: #e2e8f0;
  box-shadow: none;
  cursor: not-allowed;
  opacity: 1;
}

/* 手机端：每排始终三个等宽按钮，图标在上、文字在下。 */
@media screen and (max-width: 720px) {
  #app .study999-lesson-nav-section {
    padding: 14px 10px;
  }

  #app .study999-lesson-nav-row {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 7px;
  }

  #app .study999-lesson-nav-btn {
    flex-direction: column;
    gap: 5px;
    min-height: 68px;
    padding: 9px 3px;
    font-size: clamp(12px, 3.2vw, 14px);
    white-space: nowrap;
  }

  #app .study999-lesson-nav-btn svg {
    width: 19px;
    height: 19px;
    flex-basis: 19px;
  }
}