:root {
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --a2-color: #3b82f6;
    --b1-color: #8b5cf6;
    --bg-main: #f1f5f9;
    --bg-card: #ffffff;
    --text-main: #0f172a;
    --text-muted: #64748b;
    --border: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
    --header-height: 72px;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Inter', -apple-system, system-ui, sans-serif;
    background-color: var(--bg-main);
    color: var(--text-main);
    height: 100vh;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

/* Header */
.app-header {
    height: var(--header-height);
    background: white;
    border-bottom: 1px solid var(--border);
    display: flex;
    align-items: center;
    padding: 0 2rem;
    gap: 2rem;
    box-shadow: var(--shadow-sm);
    z-index: 100;
}

.logo {
    min-width: 200px;
}

.logo h1 {
    font-size: 1.25rem;
    font-weight: 800;
    letter-spacing: -0.025em;
    color: var(--primary);
}

.logo span {
    font-size: 0.7rem;
    text-transform: uppercase;
    font-weight: 600;
    color: var(--text-muted);
}

.search-container {
    flex: 1;
    max-width: 600px;
    position: relative;
}

#wordSearch {
    width: 100%;
    padding: 0.75rem 1rem 0.75rem 2.75rem;
    background: var(--bg-main);
    border: 1px solid transparent;
    border-radius: 10px;
    font-size: 0.95rem;
    transition: all 0.2s;
}

#wordSearch:focus {
    background: white;
    border-color: var(--primary);
    box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.1);
    outline: none;
}

.search-icon {
    position: absolute;
    left: 1rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
    pointer-events: none;
}

.clear-btn {
    position: absolute;
    right: 0.75rem;
    top: 50%;
    transform: translateY(-50%);
    background: #e2e8f0;
    border: none;
    border-radius: 50%;
    width: 24px;
    height: 24px;
    display: none;
    align-items: center;
    justify-content: center;
    color: var(--text-muted);
    cursor: pointer;
    transition: all 0.2s;
    padding: 0;
}

.clear-btn:hover {
    background: #cbd5e1;
    color: var(--text-main);
    transform: translateY(-50%) scale(1.1);
}

.clear-btn svg {
    width: 14px;
    height: 14px;
}

/* Layout */
.app-body {
    display: flex;
    flex: 1;
    overflow: hidden;
}

.sidebar {
    width: 300px;
    background: white;
    border-right: 1px solid var(--border);
    padding: 2rem 2rem 4rem 2rem;
    display: flex;
    flex-direction: column;
    gap: 2.5rem;
    overflow-y: auto;
}

.content-area {
    flex: 1;
    padding: 2rem;
    overflow-y: auto;
    scroll-behavior: smooth;
}

/* Sidebar Groups */
.filter-group h3 {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-muted);
    margin-bottom: 1rem;
}

.checkbox-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.checkbox-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: color 0.2s;
}

.checkbox-item:hover { color: var(--primary); }

.checkbox-item input {
    width: 18px;
    height: 18px;
    accent-color: var(--primary);
    cursor: pointer;
}

.alphabet-filter-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0.5rem;
}

.alphabet-checkbox {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 4px;
    border: 1px solid var(--border);
    border-radius: 6px;
    font-size: 0.75rem;
    font-weight: 700;
    cursor: pointer;
    transition: all 0.2s;
}

.alphabet-checkbox:hover {
    border-color: var(--primary);
    background: #eff6ff;
}

.alphabet-checkbox input { display: none; }

.alphabet-checkbox.selected {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

/* Custom Dropdown */
.topic-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
}

#clearTopics, #clearAlphabets {
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--primary);
    background: #eff6ff;
    border: none;
    padding: 4px 8px;
    border-radius: 4px;
    cursor: pointer;
    transition: all 0.2s;
}

#clearTopics:hover, #clearAlphabets:hover {
    background: var(--primary);
    color: white;
}

.custom-dropdown { position: relative; }

.dropdown-selected {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 1rem;
    background: white;
    border: 1px solid var(--border);
    border-radius: 10px;
    font-size: 0.9rem;
    cursor: pointer;
    transition: border-color 0.2s;
}

.dropdown-selected:hover { border-color: var(--text-muted); }

.dropdown-menu {
    position: absolute;
    top: calc(100% + 8px);
    left: 0;
    width: 100%;
    background: white;
    border: 1px solid var(--border);
    border-radius: 12px;
    box-shadow: 0 20px 25px -5px rgb(0 0 0 / 0.1);
    z-index: 50;
    display: none;
    flex-direction: column;
    padding: 0.5rem;
}

.dropdown-menu.show { display: flex; }

#topicSearch {
    padding: 0.6rem;
    border: 1px solid var(--border);
    border-radius: 6px;
    margin-bottom: 0.5rem;
    font-size: 0.85rem;
}

.topic-scroll {
    max-height: 320px;
    overflow-y: auto;
}

.topic-scroll .checkbox-item {
    padding: 8px;
    border-radius: 6px;
}

.topic-scroll .checkbox-item:hover { background: var(--bg-main); }

/* Abbreviations Legend */
.abbreviations-section {
    padding-top: 0;
}

.abbrev-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 0.4rem;
}

.abbrev-item {
    font-size: 0.75rem;
    color: var(--text-muted);
    display: flex;
    gap: 0.5rem;
}

.abbrev-item span {
    font-weight: 700;
    color: var(--text-main);
    min-width: 50px;
}

/* Word Grid */
.stats-bar {
    margin-bottom: 1.5rem;
    font-size: 0.875rem;
    color: var(--text-muted);
    font-weight: 500;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.copy-all-btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    background: var(--primary);
    color: white;
    border: none;
    padding: 6px 14px;
    border-radius: 8px;
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

.copy-all-btn:hover { background: var(--primary-hover); transform: translateY(-1px); }
.copy-all-btn:active { transform: translateY(0); }
.copy-all-btn.copied { background: #10b981; }

.grid-container {
    display: flex;
    position: relative;
    gap: 1rem;
}

.word-grid {
    flex: 1;
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 1.25rem;
    align-content: start;
}

.alphabet-nav {
    position: sticky;
    top: 0;
    right: 0;
    height: calc(100vh - var(--header-height) - 100px);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    padding: 0.5rem;
    background: white;
    border-radius: 20px;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border);
    font-size: 0.65rem;
    font-weight: 700;
    color: var(--text-muted);
}

.alphabet-nav span {
    cursor: pointer;
    padding: 2px 4px;
    border-radius: 4px;
    text-align: center;
    transition: all 0.2s;
}

.alphabet-nav span:hover {
    color: var(--primary);
    background: #eff6ff;
}

.alphabet-nav span.inactive {
    opacity: 0.2;
    pointer-events: none;
}

.word-card {
    background: white;
    border: 1px solid var(--border);
    border-radius: 16px;
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.word-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
    border-color: transparent;
}

.word-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
}

.word-title-group {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.fav-btn {
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px;
    display: flex;
    align-items: center;
    color: #cbd5e1;
    transition: all 0.2s;
}

.fav-btn:hover { color: #f43f5e; transform: scale(1.1); }
.fav-btn.is-favorite { color: #f43f5e; }

.word-title {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-main);
}

.copy-btn {
    opacity: 0;
    background: var(--bg-main);
    border: none;
    padding: 6px;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
    color: var(--text-muted);
}

.word-card:hover .copy-btn { opacity: 1; }
.copy-btn:hover { background: #e2e8f0; color: var(--primary); }

.level-badges { display: flex; gap: 0.5rem; }

.badge {
    font-size: 0.65rem;
    font-weight: 800;
    padding: 4px 10px;
    border-radius: 6px;
}

.badge-a2 { background: #dbeafe; color: #1d4ed8; }
.badge-b1 { background: #f3e8ff; color: #7e22ce; }

.word-topics {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.topic-tag {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-muted);
    background: var(--bg-main);
    padding: 4px 12px;
    border-radius: 20px;
}

/* Auth Modal */
.auth-modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--bg-main);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
}

.auth-card {
    background: white;
    padding: 2.5rem;
    border-radius: 20px;
    box-shadow: 0 20px 25px -5px rgb(0 0 0 / 0.1);
    max-width: 400px;
    width: 90%;
    text-align: center;
    border: 1px solid var(--border);
}

.auth-card h2 {
    margin-bottom: 0.5rem;
    color: var(--text-main);
}

.auth-card p {
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-bottom: 1.5rem;
}

.auth-card input {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 1px solid var(--border);
    border-radius: 10px;
    margin-bottom: 1rem;
    font-size: 1rem;
    text-align: center;
}

.auth-card button {
    width: 100%;
    padding: 0.75rem;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 10px;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s;
}

.auth-card button:hover { background: var(--primary-hover); }

.auth-error {
    color: #ef4444 !important;
    margin-top: 1rem;
    font-weight: 600;
    display: none;
}

.auth-modal.hidden { display: none; }

/* Responsive & Scroll Spy */
.alphabet-nav span.active {
    color: var(--primary);
    background: #eff6ff;
    transform: scale(1.2);
    font-weight: 900;
}

.menu-toggle {
    display: none;
    background: none;
    border: none;
    color: var(--text-main);
    cursor: pointer;
    padding: 0.5rem;
    margin-left: -0.5rem;
}

.sidebar-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.4);
    backdrop-filter: blur(4px);
    z-index: 150;
    display: none;
}

@media (max-width: 768px) {
    .app-header {
        padding: 0 1rem;
        gap: 1rem;
    }

    .logo { min-width: auto; }
    .logo h1 { font-size: 1.1rem; }
    .logo span { display: none; }

    .menu-toggle { display: block; }

    .sidebar {
        position: fixed;
        top: 0;
        left: -100%;
        height: 100vh;
        z-index: 200;
        transition: left 0.3s cubic-bezier(0.4, 0, 0.2, 1);
        box-shadow: 20px 0 25px -5px rgba(0, 0, 0, 0.1);
    }

    .sidebar.show { left: 0; }
    .sidebar-overlay.show { display: block; }

    .content-area { padding: 1rem; }

    .word-grid {
        grid-template-columns: 1fr;
    }

    .stats-bar {
        flex-direction: column;
        align-items: flex-start;
        gap: 1rem;
    }

    .alphabet-nav {
        display: none !important; /* Hide alphabet nav on small mobile */
    }
}

@media (max-width: 480px) {
    .search-container {
        max-width: none;
    }
    #wordSearch {
        padding-left: 2.25rem;
        font-size: 0.85rem;
    }
    .search-icon { left: 0.75rem; }
}

/* Scrollbar styling for drawer */
.sidebar::-webkit-scrollbar { width: 4px; }