/* ==========================================================================
   difficulty.css — 难度选择页（文档 §8.2）
   ========================================================================== */

.difficulty {
  height: 100%;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: clamp(18px, 3vh, 30px);
  width: min(1040px, 100%);
  margin: 0 auto;
  padding: clamp(20px, 4vh, 44px) var(--s-4);
  overflow-y: auto;
}

.difficulty__head {
  text-align: center;
}

.difficulty__eyebrow {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.28em;
  color: var(--c-ink-faint);
  text-transform: uppercase;
}

.difficulty__title {
  margin-top: 6px;
  font-size: clamp(24px, 3vw, 32px);
  font-weight: 800;
  letter-spacing: 0.04em;
  color: var(--c-ink);
}

.difficulty__hint {
  margin-top: 6px;
  font-size: 13px;
  color: var(--c-ink-soft);
}

/* ---------- 卡片区 ---------- */
.difficulty__cards {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: clamp(10px, 1.6vw, 18px);
  align-items: stretch;
}

.diffcard {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 10px;
  /* 顶部留白固定，保证三张卡的标题在同一水平线上（推荐角标是绝对定位的） */
  padding: 42px 18px 16px;
  text-align: left;
  border: 1.5px solid var(--c-line);
  border-radius: var(--r-lg);
  background: #ffffff;
  color: var(--c-ink);
  cursor: pointer;
  transition: transform var(--t-fast), border-color var(--t-base),
    box-shadow var(--t-base), background-color var(--t-base);
}

.diffcard:hover {
  transform: translateY(-3px);
  border-color: var(--c-pink);
  box-shadow: 0 20px 36px -26px rgba(236, 143, 182, 0.95);
}

.diffcard.is-selected {
  border-color: var(--c-pink-deep);
  border-width: 2px;
  background: linear-gradient(180deg, #fffafd 0%, #ffffff 60%);
  box-shadow: 0 24px 44px -28px rgba(236, 143, 182, 0.95);
}

/* 选中标记 */
.diffcard.is-selected::after {
  content: "";
  position: absolute;
  top: 14px;
  right: 14px;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--c-pink-deep)
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23fff' stroke-width='3.4' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M5 13l4 4 10-10'/%3E%3C/svg%3E")
    center / 11px no-repeat;
  box-shadow: 0 4px 10px -4px rgba(236, 143, 182, 1);
}

/* 推荐角标 */
.diffcard__badge {
  position: absolute;
  top: 14px;
  left: 18px;
  padding: 2px 9px;
  border-radius: var(--r-pill);
  background: linear-gradient(135deg, var(--c-pink) 0%, var(--c-lilac) 100%);
  color: #4a2334;
  font-size: 10.5px;
  font-weight: 800;
  letter-spacing: 0.08em;
}

.diffcard__head {
  display: flex;
  align-items: baseline;
  gap: 8px;
}

.diffcard__name {
  font-size: 21px;
  font-weight: 800;
  letter-spacing: 0.04em;
}

.diffcard__en {
  font-size: 10.5px;
  font-weight: 700;
  letter-spacing: 0.16em;
  color: var(--c-ink-faint);
}

.diffcard__desc {
  /* 预留两行高度，保证三张卡的参数表从同一水平线开始 */
  min-height: 3em;
  font-size: 12.5px;
  line-height: 1.5;
  color: var(--c-ink-soft);
}

.diffcard__stats {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 6px;
  border-top: 1px dashed #f2e2ec;
  padding-top: 10px;
}

.diffcard__stat {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
}

.diffcard__statlabel {
  font-size: 11.5px;
  color: var(--c-ink-faint);
  letter-spacing: 0.02em;
}

.diffcard__statvalue {
  font-size: 13px;
  font-weight: 700;
  color: var(--c-ink);
}

/* ---------- 底部按钮 ---------- */
.difficulty__foot {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--s-2);
}

.difficulty__foot .btn--lg {
  min-width: 200px;
}

/* 窄屏：卡片改单列 */
@media (max-width: 860px) {
  .difficulty__cards {
    grid-template-columns: 1fr;
  }
  .diffcard__desc {
    min-height: 0;
  }
}