/* ============================================================
   MODULE: Nghe viết bài khóa — layout 2 cột (sidebar + quiz)
   Thiết kế lấp đầy chiều rộng trên desktop, thu gọn 1 cột trên mobile.
   ============================================================ */
.nv-shell {
  display: grid;
  grid-template-columns: 300px 1fr;
  gap: var(--space-4);
  align-items: start;
}
@media (max-width: 860px) {
  .nv-shell { grid-template-columns: 1fr; }
}

/* --- Sidebar --- */
.nv-sidebar {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-3);
  position: sticky;
  top: calc(var(--header-height) + var(--space-3));
  max-height: calc(100vh - var(--header-height) - var(--space-5));
  overflow-y: auto;
}
@media (max-width: 860px) {
  .nv-sidebar { position: static; max-height: none; }
}
.nv-curr-tabs { display: flex; gap: var(--space-2); margin-bottom: var(--space-3); flex-wrap: wrap; }
.nv-curr-tab {
  flex: 1;
  min-width: 90px;
  text-align: center;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: var(--space-2);
  font-size: var(--font-size-sm);
  font-weight: 600;
  cursor: pointer;
  background: var(--color-surface);
  color: var(--color-text-muted);
}
.nv-curr-tab.is-active.curr-hsk { background: var(--curr-hsk-bg); color: var(--curr-hsk); border-color: var(--curr-hsk); }
.nv-curr-tab.is-active.curr-boya { background: var(--curr-boya-bg); color: var(--curr-boya); border-color: var(--curr-boya); }
.nv-curr-tab.is-active.curr-hanngu { background: var(--curr-hanngu-bg); color: var(--curr-hanngu); border-color: var(--curr-hanngu); }

.nv-lesson-list { display: flex; flex-direction: column; gap: var(--space-1); }
.nv-lesson-item {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2);
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: var(--font-size-sm);
  border-left: 3px solid transparent;
}
.nv-lesson-item:hover { background: var(--color-surface-alt); }
.nv-lesson-item.is-selected { background: var(--color-surface-alt); font-weight: 600; }
.nv-lesson-item.curr-hsk.is-selected { border-left-color: var(--curr-hsk); }
.nv-lesson-item.curr-boya.is-selected { border-left-color: var(--curr-boya); }
.nv-lesson-item.curr-hanngu.is-selected { border-left-color: var(--curr-hanngu); }
.nv-lesson-item__count { margin-left: auto; color: var(--color-text-muted); font-size: 0.75rem; }
.nv-lesson-checkbox { flex-shrink: 0; width: 16px; height: 16px; cursor: pointer; }

.curr-badge {
  display: inline-block; padding: 2px 10px; border-radius: var(--radius-full);
  font-size: var(--text-caption); font-weight: 600; background: var(--color-surface-alt); color: var(--color-text-muted);
}
.curr-badge.curr-hsk { background: var(--curr-hsk-bg); color: var(--curr-hsk); }
.curr-badge.curr-boya { background: var(--curr-boya-bg); color: var(--curr-boya); }
.curr-badge.curr-hanngu { background: var(--curr-hanngu-bg); color: var(--curr-hanngu); }

/* --- Hội thoại luyện nghe (mẫu, tự biên soạn theo quyển) --- */
.nv-dialogue-box {
  background: var(--color-surface-alt); border: 1px solid var(--color-border);
  border-radius: var(--radius-md); padding: var(--space-3); margin-bottom: var(--space-4);
}
.nv-dialogue-box__title { font-weight: 700; font-size: var(--text-body-sm); margin-bottom: var(--space-2); }
.nv-dialogue-line { display: flex; gap: var(--space-2); align-items: flex-start; margin-bottom: var(--space-2); }
.nv-dialogue-play {
  flex-shrink: 0; width: 32px; height: 32px; border-radius: 50%;
  border: 1px solid var(--color-border); background: var(--color-surface); cursor: pointer; font-size: 0.9rem;
}
.nv-dialogue-line__hanzi { font-family: var(--font-family-display), "Noto Sans SC", sans-serif; font-size: var(--text-body); color: var(--color-text); }
.nv-dialogue-line__pinyin { color: var(--color-primary); font-size: var(--text-caption); font-weight: 600; }
.nv-dialogue-line__meaning { color: var(--color-text-muted); font-size: var(--text-caption); }

/* --- Main quiz area --- */
.nv-main {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
  min-height: 420px;
}
.nv-empty-state { text-align: center; color: var(--color-text-muted); padding: var(--space-6) var(--space-3); }
.nv-empty-state__icon { font-size: 3rem; margin-bottom: var(--space-2); }

.nv-lives-picker { display: flex; gap: var(--space-2); margin-bottom: var(--space-4); }
.nv-lives-picker button {
  border: 1px solid var(--color-border);
  background: var(--color-surface);
  border-radius: var(--radius-sm);
  padding: var(--space-2) var(--space-3);
  cursor: pointer;
  font-size: var(--font-size-sm);
}
.nv-lives-picker button.is-active { background: var(--color-primary); border-color: var(--color-primary); color: var(--color-text-on-primary); }

.nv-quiz-top { display: flex; justify-content: space-between; align-items: center; margin-bottom: var(--space-3); }
.nv-quiz-body { display: grid; grid-template-columns: 1fr 240px; gap: var(--space-5); }
@media (max-width: 700px) { .nv-quiz-body { grid-template-columns: 1fr; } }

.nv-canvas { border: 1px solid var(--color-border); border-radius: var(--radius-md); background: var(--color-surface-alt); touch-action: none; cursor: crosshair; }
.nv-side-panel { display: flex; flex-direction: column; gap: var(--space-3); align-items: center; text-align: center; }

.nv-result { text-align: center; padding: var(--space-4) 0; }
.nv-result__score { font-size: 3rem; font-weight: 700; color: var(--color-primary); }

.nv-explain-box {
  background: linear-gradient(135deg, rgba(192,57,43,0.06), rgba(44,95,111,0.06));
  border-left: 4px solid var(--color-primary);
  border-radius: var(--radius-sm);
  padding: var(--space-3);
  font-size: var(--font-size-sm);
  color: var(--color-text);
  line-height: 1.7;
}

/* ---------------------------- PHÂN TÍCH LỖI TỪNG CHỮ (Mục V/VI/XXIV) ---------------------------- */
.nv-diff-row { display: flex; flex-wrap: wrap; gap: 4px; margin: var(--space-2) 0; font-family: "Noto Sans SC", sans-serif; }
.nv-diff-char {
  position: relative; display: inline-flex; align-items: center; justify-content: center;
  min-width: 36px; height: 36px; font-size: 1.2rem; border-radius: var(--radius-sm); padding: 0 4px;
}
.nv-diff-char--match { background: var(--color-success-bg, rgba(34,197,94,0.12)); color: var(--color-text); }
.nv-diff-char--wrong { background: var(--color-error-bg); color: var(--color-error); flex-direction: column; height: auto; padding: 4px; }
.nv-diff-char__sub { font-size: 0.65rem; text-decoration: line-through; color: var(--color-text-faint); line-height: 1; }
.nv-diff-char--missing { background: var(--color-warning-bg); color: var(--color-warning); border: 1px dashed currentColor; }
.nv-diff-char--extra { background: var(--color-surface-alt); color: var(--color-text-faint); text-decoration: line-through; }
.nv-diff-legend { display: flex; gap: var(--space-3); flex-wrap: wrap; font-size: var(--text-caption); color: var(--color-text-muted); margin-top: var(--space-2); }
.nv-diff-legend span { display: inline-flex; align-items: center; gap: 4px; }
.nv-diff-legend__dot { width: 10px; height: 10px; border-radius: 3px; display: inline-block; }

/* ---------------------------- HÀNG ÔN TẬP (Mục XXI Review Queue) ---------------------------- */
.nv-review-card { margin-top: var(--space-4); }
.nv-review-list { display: flex; flex-wrap: wrap; gap: var(--space-2); }
.nv-review-chip {
  display: flex; flex-direction: column; align-items: center; gap: 2px; padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md); background: var(--color-surface); border: 1px solid var(--color-border); cursor: pointer;
  transition: transform var(--duration-fast) var(--ease-standard);
}
.nv-review-chip:hover { transform: translateY(-2px); border-color: var(--color-error); }
.nv-review-chip__char { font-size: 1.3rem; font-family: "Noto Sans SC", sans-serif; }
.nv-review-chip__count { font-size: var(--text-caption); color: var(--color-error); font-weight: 700; }

/* ---------------------------- CHẾ ĐỘ NGHE ĐIỀN TỪ (Mục VIII) ---------------------------- */
.nv-fill-sentence {
  font-family: "Noto Sans SC", sans-serif; font-size: 1.3rem; line-height: 2.2; padding: var(--space-3);
  background: var(--color-surface-alt); border-radius: var(--radius-md); word-break: break-word;
}
.nv-fill-blank {
  display: inline-block; min-width: 48px; border-bottom: 2px solid var(--color-primary); text-align: center; color: var(--color-primary);
}

/* ---------------------------- CHẾ ĐỘ SẮP XẾP CÂU (Mục IX) ---------------------------- */
.nv-order-target {
  display: flex; flex-wrap: wrap; gap: 6px; min-height: 56px; padding: var(--space-2);
  border: 2px dashed var(--color-border); border-radius: var(--radius-md); margin-bottom: var(--space-3); align-items: center;
}
.nv-order-pool { display: flex; flex-wrap: wrap; gap: 6px; }
.nv-order-chip {
  font-family: "Noto Sans SC", sans-serif; font-size: 1.05rem; padding: 8px 14px; min-height: 44px;
  border-radius: var(--radius-md); border: 1px solid var(--color-border); background: var(--color-surface); cursor: pointer;
  transition: transform var(--duration-fast) var(--ease-standard);
}
.nv-order-chip:hover { transform: translateY(-2px); border-color: var(--color-primary); }
.nv-order-chip--placed { background: var(--color-primary-soft); border-color: var(--color-primary); color: var(--color-primary); }

/* ---------------------------- CHỌN CHẾ ĐỘ LUYỆN ---------------------------- */
.nv-mode-picker button.is-active { background: var(--color-primary); color: #fff; border-color: var(--color-primary); }

/* ---------------------------- XEM MẪU NÉT VIẾT (Mục XII, giai đoạn 1) ---------------------------- */
.nv-stroke-char-picker { display: flex; gap: 6px; flex-wrap: wrap; }
.nv-stroke-char-btn {
  font-family: "Noto Sans SC", sans-serif; font-size: 1.1rem; width: 40px; height: 40px;
  border-radius: var(--radius-sm); border: 1px solid var(--color-border); background: var(--color-surface); cursor: pointer;
}
.nv-stroke-char-btn.is-active { background: var(--color-primary); color: #fff; border-color: var(--color-primary); }
#nvStrokeTarget svg { max-width: 100%; }