:root {
    --primary: #4f46e5;
    --bg-color: #f3f4f6;
    --card-bg: #ffffff;
    --text-dark: #1f2937;
    --text-gray: #6b7280;
}

* { margin: 0; padding: 0; box-sizing: border-box; font-family: 'Segoe UI', Roboto, sans-serif; }
body { background-color: var(--bg-color); color: var(--text-dark); padding-bottom: 70px; }

.app-header { background-color: var(--primary); color: white; padding: 15px 20px; position: sticky; top: 0; z-index: 100; box-shadow: 0 2px 10px rgba(0,0,0,0.1); }
.app-title { font-size: 1.2rem; font-weight: bold; margin-bottom: 10px; }
.search-bar { width: 100%; padding: 10px 15px; border-radius: 20px; border: none; outline: none; font-size: 0.9rem; }

.filters { display: flex; overflow-x: auto; padding: 15px 20px; gap: 10px; scrollbar-width: none; }
.filters::-webkit-scrollbar { display: none; }
.filter-chip { background-color: white; padding: 6px 15px; border-radius: 20px; font-size: 0.85rem; font-weight: bold; color: var(--text-dark); border: 1px solid #e5e7eb; white-space: nowrap; cursor: pointer; }
.filter-chip.active { background-color: var(--primary); color: white; border-color: var(--primary); }

.card-container { padding: 0 20px; }
.flashcard { background-color: var(--card-bg); border-radius: 15px; padding: 20px; box-shadow: 0 4px 6px rgba(0,0,0,0.05); margin-bottom: 20px; }
.card-header { display: flex; justify-content: space-between; align-items: center; border-bottom: 1px solid #f3f4f6; padding-bottom: 10px; margin-bottom: 15px; }
.word-title { font-size: 1.4rem; font-weight: 800; color: var(--primary); text-transform: uppercase;}
.word-type { font-size: 0.8rem; color: var(--text-gray); background: #e0e7ff; padding: 3px 8px; border-radius: 10px; }
.audio-btn { background-color: #f3f4f6; border: none; width: 40px; height: 40px; border-radius: 50%; font-size: 1.2rem; display: flex; align-items: center; justify-content: center; cursor: pointer; }

.meaning-title { font-weight: bold; font-size: 1.1rem; margin-bottom: 10px; }
.sentence-box { background-color: #f8fafc; padding: 12px; border-left: 4px solid var(--primary); border-radius: 0 8px 8px 0; font-size: 0.95rem; }

.table-wrapper { overflow-x: auto; margin-top: 15px; border-radius: 8px; border: 1px solid #e5e7eb; }
table { width: 100%; border-collapse: collapse; font-size: 0.85rem; text-align: left; }
th, td { padding: 8px 10px; border-bottom: 1px solid #e5e7eb; }
th { background-color: #f9fafb; font-weight: 600; }

.expand-btn { width: 100%; background: none; border: none; color: var(--primary); font-weight: bold; padding: 10px 0; margin-top: 10px; font-size: 0.9rem; cursor: pointer; }
.hidden-details { display: none; margin-top: 15px; padding-top: 15px; border-top: 1px dashed #e5e7eb; font-size: 0.9rem;}

.bottom-nav { position: fixed; bottom: 0; width: 100%; background-color: white; display: flex; justify-content: space-around; padding: 12px 0; box-shadow: 0 -2px 10px rgba(0,0,0,0.05); z-index: 100; }
.nav-item { display: flex; flex-direction: column; align-items: center; color: var(--text-gray); font-size: 0.75rem; font-weight: bold; }
.nav-item.active { color: var(--primary); }
.nav-icon { font-size: 1.4rem; margin-bottom: 3px; }