/* ==========================================================================
   Design tokens
   Dark mode is driven by [data-theme] on <html>, set by an inline script in
   header.php before the stylesheet is applied.
   ========================================================================== */
:root {
    color-scheme: light;
    --bg:           #ffffff;
    --bg-alt:       #fafafa;
    --surface:      #ffffff;
    --fg:           #1a1a1a;
    --fg-dim:       #444444;
    --fg-muted:     #666666;
    --fg-faint:     #888888;
    --fg-ghost:     #cccccc;
    --border:       #eeeeee;
    --border-soft:  #f2f2f2;
    --input-border: #dddddd;
    --accent-bg:    #000000;
    --accent-fg:    #ffffff;
    --accent-hover: #333333;
    --danger:       #ff4d4d;
    --wrong-bg:     #ffebeb;
    --wrong-border: #ffcaca;
    --shadow:       rgba(0, 0, 0, 0.05);
    --shadow-lg:    rgba(0, 0, 0, 0.08);
}

[data-theme="dark"] {
    color-scheme: dark;
    --bg:           #0f1115;
    --bg-alt:       #171a20;
    --surface:      #1c2027;
    --fg:           #e8eaed;
    --fg-dim:       #b3b8c2;
    --fg-muted:     #9aa1ad;
    --fg-faint:     #7d848f;
    --fg-ghost:     #4a505c;
    --border:       #2a2f38;
    --border-soft:  #22262e;
    --input-border: #363c47;
    --accent-bg:    #e8eaed;
    --accent-fg:    #0f1115;
    --accent-hover: #ffffff;
    --danger:       #ff6b6b;
    --wrong-bg:     #3a1d21;
    --wrong-border: #6b2f36;
    --shadow:       rgba(0, 0, 0, 0.5);
    --shadow-lg:    rgba(0, 0, 0, 0.55);
}

/* Reset & Base Styles */
* { margin: 0; padding: 0; box-sizing: border-box; }
body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg);
    color: var(--fg);
    line-height: 1.6;
    transition: background-color .25s ease, color .25s ease;
}
.container { width: 90%; max-width: 1100px; margin: 0 auto; }
a { text-decoration: none; color: inherit; transition: 0.3s; }

/* Navigation */
.main-header {
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    transition: background-color .25s ease, border-color .25s ease;
}
.navbar { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 1rem; }
.nav-right { display: flex; align-items: center; gap: 2rem; }
.logo a { font-size: 1.4rem; font-weight: 800; letter-spacing: -1px; }
.logo span { font-weight: 300; color: var(--fg-faint); }
.nav-menu { display: flex; list-style: none; gap: 2rem; flex-wrap: wrap; }
.nav-menu a { font-size: 0.9rem; font-weight: 600; color: var(--fg-muted); }
.nav-menu a.active, .nav-menu a:hover { color: var(--fg); }

/* Mode Switcher & Chips */
.mode-switcher-container {
    display: flex;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
    gap: 1.5rem;
    margin-bottom: 3rem;
    padding: 1rem;
    background: var(--bg-alt);
    border-radius: 16px;
    border: 1px solid var(--border-soft);
}

.mode-switcher {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.mode-chip {
    padding: 0.6rem 1.2rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 50px;
    font-size: 0.85rem;
    font-weight: 700;
    color: var(--fg-muted);
    transition: 0.3s;
}

.mode-chip:hover {
    border-color: var(--accent-bg);
    color: var(--fg);
}

.mode-chip.active {
    background: var(--accent-bg);
    color: var(--accent-fg);
    border-color: var(--accent-bg);
}

.topic-filter-box {
    display: flex;
    align-items: center;
    gap: 0.8rem;
    font-size: 0.9rem;
    font-weight: 600;
}

.topic-filter-box select {
    padding: 0.5rem 1rem;
    border-radius: 8px;
    border: 1px solid var(--border);
    background: var(--surface);
    color: var(--fg);
    font-family: inherit;
    font-weight: 600;
    cursor: pointer;
}

.theme-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 38px;
    height: 38px;
    background: none;
    border: 1px solid var(--border);
    border-radius: 50%;
    color: var(--fg-muted);
    cursor: pointer;
    transition: color .2s ease, border-color .2s ease;
}
.theme-toggle:hover { color: var(--fg); border-color: var(--accent-bg); }
.theme-toggle svg { width: 18px; height: 18px; display: block; }
.theme-toggle .icon-sun { display: none; }
[data-theme="dark"] .theme-toggle .icon-sun  { display: block; }
[data-theme="dark"] .theme-toggle .icon-moon { display: none; }

/* Dashboard Hero */
#dashboard-hero { padding: 3rem 0; border-bottom: 1px solid var(--border-soft); margin-bottom: 3rem; }
.stats-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 2rem; }
.stat-card {
    text-align: center;
    padding: 2rem;
    background: var(--bg-alt);
    border-radius: 12px;
}
.stat-value { display: block; font-size: 2.5rem; font-weight: 800; letter-spacing: -2px; }
.stat-label { font-size: 0.85rem; color: var(--fg-faint); text-transform: uppercase; font-weight: 700; }

/* Study Time Section (Restored & Optimized) */
.study-time-section {
    margin-bottom: 4rem;
    padding: 2.5rem;
    background: var(--bg-alt);
    border-radius: 20px;
    border: 1px solid var(--border-soft);
}
.time-grid {
    display: flex;
    gap: 1.5rem;
    margin-bottom: 3rem;
}
.time-card {
    flex: 1;
    background: var(--surface);
    padding: 1.5rem;
    border-radius: 12px;
    text-align: center;
    border: 1px solid var(--border);
    transition: all 0.3s ease;
}
.time-card:hover { border-color: var(--accent-bg); transform: translateY(-2px); }
.time-value { display: block; font-size: 1.8rem; font-weight: 800; color: var(--fg); }
.time-detail {
    display: grid;
    grid-template-columns: 1fr 320px;
    gap: 3rem;
}
.bar-chart { display: flex; flex-direction: column; gap: 0.8rem; }
.bar-row { display: flex; align-items: center; gap: 1rem; }
.bar-label { font-size: 0.75rem; font-weight: 700; color: var(--fg-muted); width: 50px; text-transform: uppercase; }
.bar-track { flex: 1; height: 12px; background: var(--surface); border-radius: 6px; overflow: hidden; border: 1px solid var(--border); }
.bar { height: 100%; background: var(--accent-bg); transition: width 0.8s ease; min-width: 4px; }
.mode-breakdown { display: flex; flex-direction: column; gap: 0.8rem; }
.mode-row {
    display: flex; justify-content: space-between; align-items: center;
    padding: 1rem 1.2rem; background: var(--surface); border: 1px solid var(--border);
    border-radius: 10px; font-size: 0.9rem;
}
.mode-name { font-weight: 600; color: var(--fg-muted); }
.mode-time { font-weight: 800; color: var(--fg); }

/* Layout Grid */
.main-grid { display: grid; grid-template-columns: 1fr 300px; gap: 3rem; }

/* Content Section */
.section-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 2rem; gap: 1rem; flex-wrap: wrap; }
.section-title { font-size: 1.8rem; font-weight: 800; letter-spacing: -1px; }

/* Buttons */
button, .btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background-color: var(--accent-bg);
    color: var(--accent-fg);
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 600;
    transition: 0.3s;
    font-family: inherit;
    gap: 8px;
}
button:hover, .btn:hover { background-color: var(--accent-hover); transform: translateY(-2px); }

/* Reset for specific button types */
button.view-all, button.speak-btn, button.delete-btn {
    display: inline-block; background: none; color: inherit; padding: 0; border: none; border-radius: 0; width: auto; height: auto; font-weight: normal; transform: none;
}
button.view-all:hover, button.speak-btn:hover, button.delete-btn:hover { background: none; transform: none; opacity: 0.7; }

/* Secondary button */
.btn-ghost {
    background: var(--bg-alt);
    color: var(--fg-muted);
    border: 1px solid var(--border);
    padding: 0.6rem 1.2rem;
    border-radius: 6px;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    transition: 0.3s;
}
.btn-ghost:hover {
    background: var(--border-soft);
    color: var(--fg);
}

.view-all { font-size: 0.9rem; font-weight: 600; color: var(--fg-muted); cursor: pointer; }
.view-all:hover { color: var(--fg); }

/* Search & Pagination */
.search-bar { display: flex; flex-wrap: wrap; align-items: center; gap: 0.75rem; margin-bottom: 2rem; }
.search-bar input[type="search"] {
    flex: 1; min-width: 220px; padding: 0.8rem 1rem; border: 1px solid var(--input-border); border-radius: 6px; background: var(--surface); color: var(--fg); font-family: inherit;
}
.pagination { display: flex; flex-wrap: wrap; justify-content: center; align-items: center; gap: 0.4rem; margin-top: 3rem; }
.pagination a, .pagination span {
    display: inline-flex; align-items: center; justify-content: center; min-width: 38px; height: 38px; padding: 0 0.7rem; background: var(--surface); border: 1px solid var(--border); border-radius: 6px; font-size: 0.85rem; font-weight: 600; color: var(--fg-muted);
}
.pagination .current { background: var(--accent-bg); border-color: var(--accent-bg); color: var(--accent-fg); }

/* Word Items */
.word-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 1.5rem; }
.word-item { padding: 1.5rem; border: 1px solid var(--border); border-radius: 12px; position: relative; transition: 0.3s; }
.word-item:hover { transform: translateY(-3px); box-shadow: 0 10px 30px var(--shadow); }
.word-item.learned { background: var(--bg-alt); border-color: var(--border-soft); opacity: 0.7; }
.word-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 0.5rem; gap: 0.5rem; }
.word-english { font-size: 1.2rem; font-weight: 700; }
.word-meaning { font-size: 1rem; color: var(--fg-dim); margin-bottom: 1rem; }
.topic-tag { font-size: 0.65rem; font-weight: 800; color: var(--fg-faint); text-transform: uppercase; margin-bottom: 0.5rem; display: block; }
.word-actions { display: flex; gap: 1rem; margin-top: 1rem; padding-top: 1rem; border-top: 1px solid var(--border-soft); align-items: center; }
.action-link { font-size: 0.75rem; font-weight: 700; }
.action-link.delete { color: var(--danger); margin-left: auto; }

/* Word Proficiency Bar */
.word-proficiency-container {
    height: 6px;
    background: var(--border-soft);
    border-radius: 3px;
    overflow: hidden;
    margin: 1rem 0;
}
.word-proficiency-fill {
    height: 100%;
    background: linear-gradient(to right, #ff4d4d, #ffc107, #4caf50);
    background-size: 1100px 100%; /* Giữ màu cố định theo tỉ lệ */
    transition: width 0.5s ease;
}
.word-proficiency-text {
    font-size: 0.65rem;
    font-weight: 800;
    color: var(--fg-faint);
    float: right;
    margin-top: -1.2rem;
}

/* Sidebar */
.side-card { background: var(--bg-alt); padding: 1.5rem; border-radius: 12px; margin-bottom: 1.5rem; }
.side-card h3 { font-size: 1rem; font-weight: 800; margin-bottom: 1.2rem; }
.quick-add-form input, .quick-add-form select, .quick-add-form button {
    width: 100%; padding: 0.8rem; border-radius: 6px; border: 1px solid var(--input-border); margin-bottom: 0.8rem; font-family: inherit; background: var(--surface); color: var(--fg);
}
.quick-add-form button { background: var(--accent-bg); color: var(--accent-fg); border: none; font-weight: 700; cursor: pointer; }
.mode-item { display: block; padding: 1rem; background: var(--surface); border: 1px solid var(--border); border-radius: 8px; margin-bottom: 0.8rem; }
.mode-item strong { display: block; font-size: 0.95rem; }
.mode-item span { font-size: 0.75rem; color: var(--fg-faint); }
.mode-item:hover { border-color: var(--accent-bg); }

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: var(--surface);
    padding: 2.5rem;
    border-radius: 16px;
    border: 1px solid var(--border);
    box-shadow: 0 20px 50px rgba(0,0,0,0.2);
    z-index: 2000;
    width: 90%;
    max-width: 500px;
}
.modal.is-open { display: block; }

.modal-form { display: flex; flex-direction: column; gap: 1rem; }
.modal-input {
    width: 100%;
    padding: 0.8rem;
    border-radius: 8px;
    border: 1px solid var(--input-border);
    background: var(--bg);
    color: var(--fg);
    font-family: inherit;
}
.modal-actions { display: flex; justify-content: flex-end; gap: 10px; margin-top: 1.5rem; }

/* Pagination */
.pagination {
    display: flex;
    justify-content: center;
    gap: 0.5rem;
    margin-top: 3rem;
}
.pagination a {
    padding: 0.5rem 1rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 6px;
    font-weight: 700;
    font-size: 0.9rem;
    color: var(--fg-muted);
}
.pagination a.current {
    background: var(--accent-bg);
    color: var(--accent-fg);
    border-color: var(--accent-bg);
}
.pagination a:hover:not(.current) {
    border-color: var(--accent-bg);
    color: var(--fg);
}

/* Topics Library */
.topic-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 1.5rem; }
.topic-card { display: block; padding: 2.5rem 2rem; background: var(--bg-alt); border-radius: 12px; text-align: center; border: 1px solid var(--border-soft); height: 100%; transition: 0.3s; position: relative; }
.topic-card:hover { border-color: var(--accent-bg); background: var(--surface); transform: translateY(-5px); box-shadow: 0 10px 20px var(--shadow); }
.topic-card h3 { font-size: 1.25rem; font-weight: 700; margin-bottom: 1rem; color: var(--fg); }
.topic-meta { font-size: 0.85rem; color: var(--fg-muted); }
.delete-topic-link { position: absolute; top: 15px; right: 15px; font-size: 0.65rem; color: var(--fg-ghost); font-weight: 700; text-transform: uppercase; }
.delete-topic-link:hover { color: var(--danger); }
.progress-mini { height: 4px; background: var(--border); border-radius: 2px; margin-top: 10px; overflow: hidden; }
.progress-fill { height: 100%; background: var(--accent-bg); transition: 0.5s; }

/* Flashcards & Quiz */
.flashcard-container { perspective: 1000px; width: 100%; max-width: 500px; height: 350px; margin: 2rem auto; }
.flashcard { position: relative; width: 100%; height: 100%; transition: 0.6s; transform-style: preserve-3d; border-radius: 20px; box-shadow: 0 20px 40px var(--shadow-lg); }
.flashcard.flipped { transform: rotateY(180deg); }
.flashcard-front, .flashcard-back { position: absolute; width: 100%; height: 100%; backface-visibility: hidden; display: flex; flex-direction: column; justify-content: center; align-items: center; padding: 2rem; border-radius: 20px; background: var(--surface); border: 1px solid var(--border); }
.flashcard-back { transform: rotateY(180deg); background: var(--bg-alt); }
.flashcard-word { font-size: 3rem; font-weight: 800; text-align: center; }
.flashcard-meaning { font-size: 1.8rem; font-weight: 700; text-align: center; }

.quiz-container { max-width: 600px; margin: 0 auto; background: var(--bg-alt); padding: 3rem; border-radius: 20px; transition: background-color .25s ease; }
.quiz-question { font-size: 1.6rem; font-weight: 800; text-align: center; margin-bottom: 2rem; }
.quiz-options { display: flex; flex-direction: column; gap: 0.8rem; }
.option-btn { width: 100%; text-align: left; padding: 1.2rem; background: var(--surface); color: var(--fg); border: 1px solid var(--border); border-radius: 8px; cursor: pointer; transition: 0.3s; font-family: inherit; }
.option-btn:hover { border-color: var(--accent-bg); transform: translateX(5px); }
.option-btn.correct { background: var(--accent-bg); color: var(--accent-fg); border-color: var(--accent-bg); }
.option-btn.wrong { background: var(--wrong-bg); border-color: var(--wrong-border); color: var(--danger); }

/* Typing Mode */
.typing-box {
    background: var(--surface);
    padding: 2.5rem;
    border-radius: 20px;
    border: 1px solid var(--border);
    box-shadow: 0 10px 30px var(--shadow);
}
.typing-meaning {
    font-size: 1.8rem;
    font-weight: 800;
    text-align: center;
    margin-bottom: 1rem;
    color: var(--fg);
}
.typing-example {
    font-size: 1rem;
    font-style: italic;
    color: var(--fg-muted);
    text-align: center;
    margin-bottom: 2rem;
}
.typing-input-row {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
}
.typing-input {
    flex: 1;
    padding: 1rem 1.5rem;
    font-size: 1.2rem;
    border-radius: 10px;
    border: 2px solid var(--input-border);
    background: var(--bg);
    color: var(--fg);
    font-family: inherit;
    text-align: center;
    transition: 0.3s;
}
.typing-input:focus {
    outline: none;
    border-color: var(--accent-bg);
}
.typing-input.correct { border-color: #4caf50; background: #e8f5e9; }
.typing-input.wrong { border-color: var(--danger); background: var(--wrong-bg); }
[data-theme="dark"] .typing-input.correct { background: #1b3320; }

.typing-feedback {
    min-height: 1.5rem;
    text-align: center;
    margin-bottom: 1.5rem;
    font-weight: 600;
}
.typing-feedback.correct { color: #4caf50; }
.typing-feedback.wrong { color: var(--danger); }

.typing-actions {
    display: flex;
    justify-content: center;
    gap: 1rem;
}

/* Matching Mode */
.match-status {
    display: flex;
    justify-content: space-between;
    margin-bottom: 2rem;
    font-weight: 700;
    color: var(--fg-muted);
}
.match-board {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
}
.match-col {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}
.match-card {
    padding: 1.2rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 12px;
    cursor: pointer;
    font-weight: 600;
    transition: 0.3s;
    text-align: center;
    font-family: inherit;
    font-size: 1rem;
    color: var(--fg);
}
.match-card:hover {
    border-color: var(--accent-bg);
    transform: translateY(-2px);
    box-shadow: 0 5px 15px var(--shadow);
}
.match-card.selected {
    background: var(--bg-alt);
    border-color: var(--accent-bg);
    border-width: 2px;
}
.match-card.matched {
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transform: scale(0.9);
}
.match-result {
    text-align: center;
    font-size: 1.5rem;
    font-weight: 800;
    margin-top: 3rem;
    padding: 2rem;
    background: var(--bg-alt);
    border-radius: 15px;
}

/* Shake Animation */
.shake { animation: shake 0.4s cubic-bezier(.36,.07,.19,.97) both; }
@keyframes shake {
    10%, 90% { transform: translate3d(-1px, 0, 0); }
    20%, 80% { transform: translate3d(2px, 0, 0); }
    30%, 50%, 70% { transform: translate3d(-4px, 0, 0); }
    40%, 60% { transform: translate3d(4px, 0, 0); }
}

/* Footer */
.main-footer { border-top: 1px solid var(--border); padding: 4rem 0; margin-top: 5rem; color: var(--fg-faint); font-size: 0.9rem; }
.footer-content { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; }
.footer-logo { font-weight: 800; color: var(--fg); }

/* Responsive */
@media (max-width: 900px) {
    .main-grid, .time-detail { grid-template-columns: 1fr; }
    .time-grid { flex-direction: column; }
    .stats-grid { grid-template-columns: 1fr; }
}
