/* ============================================================
   properties.css — 性质推导·黑板全屏画廊
   （斐波那契教学页面 · 样式封装 part 6 · 对应板块 #properties）
   结构沿用 natureFullscreen 的全屏容器模式，但视觉独立为"黑板"。
   ============================================================ */

/* ---- 性质卡"点击打开推导"角标 ----
   .fact 卡（facts-list 内）需 position:relative 以定位角标 */
.fact { position: relative; cursor: pointer; }
.fo-open {
  position: absolute;
  right: 14px; bottom: 12px;
  font-size: 0.72rem; letter-spacing: 1px;
  color: var(--gold-1);
  background: rgba(15,21,36,0.6);
  border: 1px solid var(--card-border);
  padding: 5px 12px; border-radius: 20px;
  opacity: 0; transform: translateY(6px);
  transition: opacity 0.3s, transform 0.3s;
  z-index: 2;
  pointer-events: none;
}
.fact:hover .fo-open { opacity: 1; transform: translateY(0); }

/* ---- 黑板全屏容器 ---- */
.fo-overlay {
  position: fixed; inset: 0; z-index: 240;
  display: grid; place-items: center;
  opacity: 0; visibility: hidden; pointer-events: none;
  transition: opacity 0.45s ease, visibility 0.45s;
}
.fo-overlay.show { opacity: 1; visibility: visible; pointer-events: auto; }

/* 黑板背景：直接使用 image/黑板图片.jpg 作全屏背景，去掉模糊与强压暗，让黑板清晰可见 */
.fo-bg {
  position: absolute; inset: 0;
  background: url('../image/黑板图片.jpg') center/cover no-repeat;
  filter: brightness(1.05) contrast(1.02);
}
/* 极淡的渐变遮罩，仅用于保证四周文字在边缘处的可读性，不影响黑板质感 */
.fo-bg::after {
  content: '';
  position: absolute; inset: 0;
  background: radial-gradient(ellipse at center, transparent 45%, rgba(15,21,36,0.35) 100%);
}

/* 内容板书面：半透明，让黑板背景透出，同时保证文字可读 */
.fo-content {
  position: relative; z-index: 2;
  max-width: 860px; width: 92%;
  max-height: 84vh; overflow-y: auto;
  background: rgba(10, 14, 22, 0.32);
  border: 1px solid rgba(251,191,36,0.4);
  border-radius: 20px;
  box-shadow: 0 24px 70px rgba(0,0,0,0.55);
  padding: 44px 52px 34px;
}
/* 黑板画廊内容区：细窄青色滚动条（仿 .view 统一风格），替代原生白色粗滚动条 */
.fo-content::-webkit-scrollbar { width: 6px; }
.fo-content::-webkit-scrollbar-track { background: transparent; }
.fo-content::-webkit-scrollbar-thumb {
  background: rgba(45, 212, 191, 0.35);   /* 青色半透明滑块 */
  border-radius: 50px;
}
.fo-content::-webkit-scrollbar-thumb:hover {
  background: rgba(45, 212, 191, 0.6);    /* 悬停变亮仍保持青色 */
}
.fo-content { scrollbar-width: thin; scrollbar-color: rgba(45,212,191,0.35) transparent; }
/* 粉笔金标题 */
.fo-kicker {
  text-align: center;
  letter-spacing: 4px;
  font-size: 0.75rem;
  color: var(--gold-1);
  text-transform: uppercase;
  margin-bottom: 6px;
  font-weight: 700;
}
.fo-title {
  text-align: center;
  font-family: 'Times New Roman', Georgia, serif;
  font-size: 1.9rem;
  font-weight: 800;
  color: var(--text);
  margin-bottom: 6px;
  letter-spacing: 1px;
}
.fo-state {
  text-align: center;
  font-size: 0.85rem;
  color: var(--muted);
  margin-bottom: 22px;
}

/* 结论速览条 */
.fo-claim {
  border-left: 4px solid var(--gold-1);
  background: rgba(251,191,36,0.08);
  padding: 12px 18px;
  border-radius: 0 10px 10px 0;
  font-size: 1.1rem;
  color: var(--gold-1);
  margin-bottom: 22px;
  font-weight: 600;
}

/* 分步推导 */
.fo-steps { display: flex; flex-direction: column; gap: 6px; }
.fo-step { display: flex; gap: 14px; align-items: flex-start; }
.fo-step .snum {
  flex-shrink: 0;
  width: 26px; height: 26px;
  display: grid; place-items: center;
  background: linear-gradient(135deg, var(--gold-1), var(--gold-2));
  color: #0f1524;
  border-radius: 50%;
  font-weight: 800; font-size: 0.8rem;
  margin-top: 4px;
}
.fo-step .sbody { flex: 1; }
.fo-step .sbody p { color: var(--text); font-size: 0.98rem; line-height: 1.8; margin-bottom: 6px; }
.fo-step .sbody .ml { color: var(--muted); font-size: 0.9rem; }
.fo-step .sbody .formula {
  background: rgba(15,21,36,0.55);
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: 10px;
  padding: 12px 18px;
  margin: 8px 0 10px;
  font-family: 'Times New Roman', Georgia, serif;
  text-align: center;
  color: var(--gold-1);
  font-size: 1.05rem;
}
.fo-step .sbody .formula .vars { color: var(--teal); }

/* 为什么重要 */
.fo-why {
  margin-top: 22px;
  padding-top: 16px;
  border-top: 1px dashed rgba(255,255,255,0.18);
  display: flex; gap: 12px; align-items: flex-start;
}
.fo-why .wico { font-size: 1.3rem; }
.fo-why p { color: var(--muted); font-size: 0.92rem; line-height: 1.7; }

/* 底部状态点 */
.fo-dots {
  margin-top: 26px;
  display: flex; gap: 8px; justify-content: center;
}
.fo-dot {
  width: 9px; height: 9px; border-radius: 50%;
  background: rgba(255,255,255,0.3);
  transition: background 0.3s, transform 0.3s;
}
.fo-dot.active { background: var(--gold-1); transform: scale(1.35); }

/* 左右切换 + 关闭 */
.fo-nav, .fo-close {
  position: fixed; z-index: 3;
  width: 52px; height: 52px;
  border-radius: 50%;
  border: 1px solid rgba(255,255,255,0.2);
  background: rgba(12,16,26,0.6);
  color: var(--text);
  font-size: 1.8rem; line-height: 1;
  cursor: pointer;
  backdrop-filter: blur(6px);
  transition: background 0.3s, color 0.3s;
}
.fo-nav:hover, .fo-close:hover { background: rgba(251,191,36,0.25); color: var(--gold-1); }
.fo-prev { left: 24px; top: 50%; transform: translateY(-50%); }
.fo-next { right: 24px; top: 50%; transform: translateY(-50%); }
.fo-close { top: 22px; right: 26px; }

/* 翻页滑入 */
@keyframes foSlideLeft  { from { transform: translateX(60px); opacity: 0; } to { transform: translateX(0); opacity: 1; } }
@keyframes foSlideRight { from { transform: translateX(-60px); opacity: 0; } to { transform: translateX(0); opacity: 1; } }
.fo-content.anim-left  { animation: foSlideLeft 0.4s ease; }
.fo-content.anim-right { animation: foSlideRight 0.4s ease; }

@media (max-width: 700px) {
  .fo-content { padding: 38px 24px 28px; }
  .fo-title { font-size: 1.5rem; }
  .fo-prev { left: 10px; }
  .fo-next { right: 10px; }
  .fo-close { right: 14px; top: 14px; }
}