/* ===================== FONT IMPORT ===================== */
/* Optimized font loading with font-display: swap */
@import url('https://fonts.googleapis.com/css2?family=Manrope:wght@200..800&display=swap');
@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+Thai:wght@100..900&display=swap');

/* ===================== ROOT & VARIABLES ===================== */
:root {
    /* Neutral minimal palette - soft earth tones */
    --primary-color: #6b6b6b;
    --secondary-color: #9a9a9a;
    --success-color: #7a8a7f;
    --danger-color: #a88c8c;
    --warning-color: #b8a88c;
    --bg-color: #f5f5f0;
    --card-bg: #fafaf8;
    --text-color: #3a3a3a;
    --text-muted: #8a8a8a;
    --border-color: #d8d8d0;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
    --shadow-md: 0 2px 6px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 4px 12px rgba(0, 0, 0, 0.08);
    --shadow-xl: 0 8px 24px rgba(0, 0, 0, 0.08);
}

/* ===================== RESET & BASE ===================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Manrope', 'Noto Sans Thai', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    padding: 20px;
    min-height: 100vh;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    /* Performance optimizations */
    will-change: auto;
    contain: layout style paint;
}

.container {
    max-width: 900px;
    margin: 0 auto;
}

/* ===================== LOGIN SCREEN ===================== */
.login-screen {
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.login-container {
    background: var(--card-bg);
    border-radius: 2px;
    padding: 48px 40px;
    max-width: 400px;
    width: 100%;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
    animation: fadeIn 0.5s ease;
}

.login-header {
    text-align: center;
    margin-bottom: 40px;
}

.login-header h1 {
    font-size: 1.5rem;
    color: var(--text-color);
    margin-bottom: 4px;
    font-weight: 400;
    letter-spacing: 0;
}

.login-header p {
    font-size: 0.875rem;
    color: var(--text-muted);
    font-weight: 400;
}

.login-form h2 {
    text-align: center;
    color: var(--text-color);
    margin-bottom: 30px;
    font-size: 1.5rem;
}

.input-group {
    margin-bottom: 25px;
}

.input-group label {
    display: block;
    margin-bottom: 8px;
    color: var(--text-color);
    font-weight: 400;
    font-size: 0.875rem;
}

.input-group input {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid var(--border-color);
    border-radius: 2px;
    font-size: 0.9375rem;
    transition: all 0.2s ease;
    background: var(--card-bg);
    font-family: inherit;
    color: var(--text-color);
}

.input-group input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(107, 107, 107, 0.1);
}

.input-group input::placeholder {
    color: #cbd5e1;
}

.login-form .btn-large {
    width: 100%;
    margin-top: 10px;
}

.login-hint {
    text-align: center;
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-top: 20px;
    line-height: 1.6;
}

/* ===================== HEADER ===================== */
header {
    margin-bottom: 40px;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 20px;
}

.header-actions {
    display: flex;
    gap: 10px;
    align-items: center;
}

header h1 {
    font-size: 1.5rem;
    color: var(--text-color);
    margin-bottom: 4px;
    font-weight: 400;
    letter-spacing: 0;
}

.subtitle {
    color: var(--text-muted);
    font-size: 0.875rem;
    font-weight: 400;
}

.btn-view-hidden {
    background: var(--card-bg);
    color: var(--text-color);
    padding: 8px 16px;
    font-size: 0.8125rem;
    white-space: nowrap;
    border: 1px solid var(--border-color);
    font-weight: 400;
    border-radius: 2px;
}

.btn-view-hidden:hover {
    background: var(--primary-color);
    color: var(--card-bg);
    border-color: var(--primary-color);
    transform: translateY(-1px);
    box-shadow: var(--shadow);
}

.btn-logout {
    background: var(--card-bg);
    color: var(--text-color);
    padding: 8px 16px;
    font-size: 0.8125rem;
    white-space: nowrap;
    border: 1px solid var(--border-color);
    font-weight: 400;
    border-radius: 2px;
}

.btn-logout:hover {
    background: var(--danger-color);
    color: var(--card-bg);
    border-color: var(--danger-color);
    transform: translateY(-1px);
    box-shadow: var(--shadow);
}

/* ===================== STATS ===================== */
.stats {
    display: flex;
    justify-content: space-around;
    gap: 20px;
    margin-bottom: 30px;
}

.stat-item {
    flex: 1;
    background: var(--card-bg);
    padding: 20px;
    border-radius: 2px;
    box-shadow: var(--shadow);
    text-align: center;
    border: 1px solid var(--border-color);
    transition: box-shadow 0.2s ease, border-color 0.2s ease, transform 0.2s ease;
    /* Performance optimization */
    will-change: transform;
}

.stat-item:hover {
    box-shadow: var(--shadow-md);
    border-color: var(--primary-color);
    transform: translateY(-2px);
}

.stat-label {
    display: block;
    color: var(--text-muted);
    font-size: 0.75rem;
    margin-bottom: 8px;
    font-weight: 400;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.stat-value {
    display: block;
    font-size: 2rem;
    font-weight: 300;
    color: var(--text-color);
}

/* ===================== FLASHCARD ===================== */
.flashcard-container {
    min-height: 400px;
    margin-bottom: 30px;
}

.flashcard {
    background: var(--card-bg);
    border-radius: 3px;
    padding: 60px 40px;
    box-shadow: var(--shadow-md);
    transition: box-shadow 0.3s ease;
    border: 1px solid var(--border-color);
    position: relative;
    /* Performance optimization */
    will-change: box-shadow;
}

.flashcard:hover {
    box-shadow: var(--shadow-lg);
}

.card-front {
    text-align: center;
    margin-bottom: 32px;
    padding-bottom: 32px;
    border-bottom: 1px solid var(--border-color);
}

.word {
    font-size: 5rem;
    color: var(--text-color);
    font-weight: 300;
    margin: 0;
    letter-spacing: -0.02em;
    animation: wordAppear 0.5s ease;
    white-space: nowrap;
    max-width: 100%;
    transition: font-size 0.3s ease;
}

/* Auto-scale font size based on word length */
.word[data-length="long"] {
    font-size: 3.8rem;
}

.word[data-length="very-long"] {
    font-size: 3rem;
}

.word[data-length="extra-long"] {
    font-size: 2.2rem;
}

@keyframes wordAppear {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.translation {
    font-size: 1.3rem;
    line-height: 1.8;
}

.translation strong {
    color: var(--text-muted);
    display: block;
    margin-bottom: 12px;
    font-size: 1rem;
}

.translation p {
    color: var(--text-color);
    font-weight: 500;
    max-width: 100%;
    overflow-wrap: break-word;
    word-wrap: break-word;
}

/* ===================== TRANSLATION TOGGLE ===================== */
.translation-section {
    display: flex;
    align-items: center;
    gap: 12px;
    margin: 24px 0;
    padding: 16px;
    background: rgba(107, 107, 107, 0.03);
    border-radius: 2px;
    border: 1px solid var(--border-color);
}

.toggle-label {
    font-weight: 600;
    color: var(--text-color);
    font-size: 1.05rem;
}

/* Toggle Switch */
.switch {
    position: relative;
    display: inline-block;
    width: 50px;
    height: 28px;
}

.switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--border-color);
    transition: 0.3s;
    border-radius: 28px;
}

.slider:before {
    position: absolute;
    content: "";
    height: 20px;
    width: 20px;
    left: 4px;
    bottom: 4px;
    background-color: var(--card-bg);
    transition: 0.3s;
    border-radius: 50%;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.15);
}

input:checked + .slider {
    background: var(--success-color);
}

input:checked + .slider:before {
    transform: translateX(22px);
}

.slider:active {
    transform: scale(0.95);
}

/* ===================== TRANSLATION CONTENT ===================== */
.translation-content {
    /* background: var(--primary-color); */
    padding: 24px;
    border-radius: 2px;
    margin-top: 16px;
    box-shadow: var(--shadow);
    animation: slideDown 0.3s ease;
    border: 1px solid var(--border-color);
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.translation-content .translation {
    color: #000000;
}

.translation-content strong {
    color: rgba(92, 92, 92, 0.95) !important;
    font-size: 1rem;
    font-weight: 400;
}

.translation-content p {
    color: rgb(0, 0, 0) !important;
    font-size: 1.5rem;
    font-weight: 500;
    max-width: 100%;
    overflow-wrap: break-word;
    word-wrap: break-word;
}

/* ===================== EMPTY STATE ===================== */
.empty-state {
    background: var(--card-bg);
    border-radius: 3px;
    padding: 60px 40px;
    text-align: center;
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
}

.empty-state p {
    font-size: 1.3rem;
    color: var(--text-color);
    margin-bottom: 10px;
    font-weight: 600;
}

.empty-state p:first-child {
    font-size: 3rem;
}

/* ===================== BUTTONS ===================== */
.actions {
    display: flex;
    flex-direction: column;
    gap: 15px;
    align-items: center;
}

.action-group {
    display: flex;
    gap: 15px;
    width: 100%;
    justify-content: center;
    flex-wrap: wrap;
}

.btn {
    padding: 10px 20px;
    border: 1px solid var(--border-color);
    border-radius: 2px;
    font-size: 0.875rem;
    font-weight: 400;
    cursor: pointer;
    transition: box-shadow 0.2s ease, transform 0.2s ease, background-color 0.2s ease;
    box-shadow: var(--shadow);
    /* Performance optimization */
    will-change: transform;
}

.btn:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-1px);
}

.btn:active {
    transform: translateY(0);
    box-shadow: var(--shadow);
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
    will-change: auto;
}

.btn-primary {
    background: var(--primary-color);
    color: var(--card-bg);
    border-color: var(--primary-color);
}

.btn-primary:hover {
    background: var(--secondary-color);
    border-color: var(--secondary-color);
}

.btn-secondary {
    background: var(--card-bg);
    color: var(--text-color);
    border-color: var(--border-color);
}

.btn-secondary:hover {
    background: var(--secondary-color);
    color: var(--card-bg);
    border-color: var(--secondary-color);
}

.btn-success {
    background: var(--success-color);
    color: var(--card-bg);
    border-color: var(--success-color);
}

.btn-success:hover {
    background: #8a9a8f;
    border-color: #8a9a8f;
}

.btn-danger {
    background: var(--card-bg);
    color: var(--text-color);
    border-color: var(--border-color);
}

.btn-danger:hover {
    background: var(--danger-color);
    color: var(--card-bg);
    border-color: var(--danger-color);
}

.btn-large {
    padding: 12px 24px;
    font-size: 0.9375rem;
    border-radius: 2px;
}

/* ===================== MODAL ===================== */
.modal {
    display: none;
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.6);
    backdrop-filter: blur(4px);
    justify-content: center;
    align-items: center;
    animation: fadeIn 0.2s ease;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.modal-content {
    background: var(--card-bg);
    border-radius: 3px;
    width: 90%;
    max-width: 500px;
    max-height: 80vh;
    display: flex;
    flex-direction: column;
    box-shadow: var(--shadow-xl);
    animation: slideUp 0.3s ease;
    border: 1px solid var(--border-color);
}

@keyframes slideUp {
    from {
        transform: translateY(50px);
        opacity: 0;
    }
    to {
        transform: translateY(0);
        opacity: 1;
    }
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 24px 28px;
    border-bottom: 1px solid var(--border-color);
}

.modal-header h2 {
    margin: 0;
    color: var(--text-color);
    font-size: 1rem;
    font-weight: 400;
}

.modal-close {
    background: none;
    border: none;
    font-size: 2rem;
    color: var(--text-muted);
    cursor: pointer;
    line-height: 1;
    padding: 0;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 8px;
    transition: all 0.2s ease;
}

.modal-close:hover {
    background: var(--border-color);
    color: var(--text-color);
}

.modal-body {
    padding: 20px 30px 30px;
    overflow-y: auto;
    flex: 1;
}

.loading,
.empty-message {
    text-align: center;
    color: var(--text-muted);
    padding: 40px 20px;
    font-size: 1.1rem;
}

/* Skeleton Loading */
.loading-skeleton {
    display: flex;
    flex-direction: column;
    gap: 12px;
    padding: 20px;
}

.skeleton-item {
    height: 60px;
    background: linear-gradient(90deg, 
        var(--border-color) 25%, 
        rgba(216, 216, 208, 0.5) 50%, 
        var(--border-color) 75%);
    background-size: 200% 100%;
    animation: shimmer 1.5s infinite;
    border-radius: 2px;
}

@keyframes shimmer {
    0% {
        background-position: 200% 0;
    }
    100% {
        background-position: -200% 0;
    }
}

/* Learned count badge */
.learned-count-badge {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    padding: 16px 20px;
    margin-bottom: 20px;
    background: var(--primary-color);
    border-radius: 2px;
    box-shadow: var(--shadow);
    border: 1px solid var(--primary-color);
}

.count-icon {
    font-size: 1.25rem;
}

.count-text {
    font-size: 0.875rem;
    color: white;
    font-weight: 400;
}

.count-number {
    font-size: 1.125rem;
    color: white;
    font-weight: 400;
    padding: 4px 12px;
    background: rgba(255, 255, 255, 0.15);
    border-radius: 0;
    min-width: 40px;
    text-align: center;
}

.hidden-words-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.hidden-word-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 14px 16px;
    background: var(--card-bg);
    border-radius: 2px;
    border: 1px solid var(--border-color);
    gap: 12px;
    transition: all 0.2s ease;
    margin-bottom: 8px;
}

.hidden-word-item:last-child {
    margin-bottom: 0;
}

.hidden-word-item:hover {
    background: rgba(107, 107, 107, 0.03);
    box-shadow: var(--shadow);
    transform: translateX(2px);
}

.word-info {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 5px;
}

.word-info strong {
    font-size: 0.9375rem;
    color: var(--text-color);
    font-weight: 400;
}

.translation-small {
    color: var(--text-muted);
    font-size: 0.8125rem;
}

.btn-unhide {
    background: var(--card-bg);
    color: var(--text-color);
    padding: 6px 12px;
    font-size: 0.8125rem;
    white-space: nowrap;
    border-radius: 2px;
    border: 1px solid var(--border-color);
}

.btn-unhide:hover {
    background: var(--success-color);
    color: var(--card-bg);
    border-color: var(--success-color);
}

/* ===================== FOOTER ===================== */
footer {
    text-align: center;
    margin-top: 48px;
    padding: 20px;
    background: transparent;
    border-radius: 0;
    border: none;
    border-top: 1px solid var(--border-color);
    color: var(--text-muted);
    font-size: 0.8125rem;
}

.count-number {
    font-size: 1.125rem;
    color: var(--card-bg);
    font-weight: 400;
    padding: 4px 12px;
    background: rgba(255, 255, 255, 0.2);
    border-radius: 2px;
    min-width: 40px;
    text-align: center;
}

footer code {
    background: transparent;
    padding: 0;
    border-radius: 0;
    font-size: 0.8125rem;
    font-weight: 400;
    color: var(--text-muted);
}

.note {
    font-size: 0.85rem;
    margin-top: 10px;
    font-style: italic;
}

/* ===================== RESPONSIVE ===================== */
@media (max-width: 768px) {
    body {
        padding: 16px;
    }

    .container {
        max-width: 100%;
    }

    .login-container {
        padding: 32px 24px;
        max-width: 100%;
    }

    .login-header h1 {
        font-size: 1.25rem;
    }

    .login-header p {
        font-size: 0.8125rem;
    }

    .header-content {
        flex-direction: column;
        align-items: stretch;
        gap: 16px;
    }

    .header-actions {
        width: 100%;
        gap: 8px;
    }

    .btn-view-hidden,
    .btn-logout {
        width: 100%;
        justify-content: center;
        padding: 10px 16px;
        font-size: 0.8125rem;
    }

    header {
        margin-bottom: 32px;
    }

    header h1 {
        font-size: 1.25rem;
    }

    .subtitle {
        font-size: 0.8125rem;
    }

    .stats {
        flex-direction: column;
        gap: 12px;
    }

    .stat-item {
        padding: 16px;
    }

    .stat-label {
        font-size: 0.6875rem;
    }

    .stat-value {
        font-size: 1.75rem;
    }

    .flashcard {
        padding: 32px 24px;
    }

    .word {
        font-size: 2rem;
    }

    .translation-section {
        padding: 12px;
        margin: 16px 0;
    }

    .toggle-label {
        font-size: 0.875rem;
    }

    .translation-content {
        padding: 20px;
    }

    .translation-content p {
        font-size: 1.125rem;
    }

    .action-group {
        flex-direction: column;
        width: 100%;
        gap: 10px;
    }

    .btn {
        padding: 12px 20px;
        font-size: 0.875rem;
    }

    .btn-success,
    .btn-danger,
    .btn-secondary {
        flex: none;
        width: 100%;
    }

    .modal-content {
        width: 95%;
        max-width: 95%;
        max-height: 90vh;
    }

    .modal-header {
        padding: 20px;
    }

    .modal-header h2 {
        font-size: 0.9375rem;
    }

    .modal-body {
        padding: 16px 20px 20px;
    }

    .learned-count-badge {
        padding: 12px 16px;
        margin-bottom: 16px;
    }

    .count-icon {
        font-size: 1.125rem;
    }

    .count-text {
        font-size: 0.8125rem;
    }

    .count-number {
        font-size: 1rem;
    }

    .hidden-word-item {
        flex-direction: row;
        padding: 12px 14px;
        gap: 10px;
    }

    .word-info strong {
        font-size: 0.875rem;
    }

    .translation-small {
        font-size: 0.75rem;
    }

    .btn-unhide {
        padding: 6px 12px;
        font-size: 0.75rem;
        white-space: nowrap;
        flex-shrink: 0;
    }

    footer {
        margin-top: 32px;
        padding: 16px;
        font-size: 0.75rem;
    }
}

@media (max-width: 480px) {
    body {
        padding: 12px;
    }

    .login-container {
        padding: 28px 20px;
    }

    .login-header h1 {
        font-size: 1.125rem;
    }

    header h1 {
        font-size: 1.125rem;
    }

    .word {
        font-size: 5rem;
    }

    .flashcard {
        padding: 28px 20px;
    }

    .stat-value {
        font-size: 1.5rem;
    }

    .btn {
        padding: 10px 16px;
    }

    .hidden-word-item {
        flex-direction: column;
        align-items: stretch;
    }

    .btn-unhide {
        width: 100%;
    }
}