/* Root Variables - Light Theme (Default) */
:root {
    --foreground: #5C6A72;
    --red: #F85552;
    --orange: #F57D26;
    --yellow: #DFA000;
    --green: #8DA101;
    --blue: #3A94C5;
    --aqua: #35A77C;
    --purple: #DF69BA;
    --bg-dim: #EFEBD4;
    --bg-0: #FDF6E3;
    --bg-1: #F4F0D9;
    --bg-2: #EFEBD4;
    --bg-3: #E6E2CC;
    --bg-4: #E0DCC7;
    --bg-5: #BDC3AF;
    --bg-red: #FBE3DA;
    --bg-visual: #EAEDC8;
    --bg-yellow: #FAEDCD;
    --bg-green: #F0F1D2;
    --bg-blue: #E9F0E9;
    --gray-0: #A6B0A0;
    --gray-1: #939F91;
    --gray-2: #829181;
}

/* Dark Theme */
[data-theme="dark"] {
    --foreground: #D3C6AA;
    --red: #E67E80;
    --orange: #E69875;
    --yellow: #DBBC7F;
    --green: #A7C080;
    --blue: #7FBBB3;
    --aqua: #83C092;
    --purple: #D699B6;
    --bg-dim: #232A2E;
    --bg-0: #2D353B;
    --bg-1: #343F44;
    --bg-2: #3D484D;
    --bg-3: #475258;
    --bg-4: #4F585E;
    --bg-5: #56635F;
    --bg-red: #543A48;
    --bg-visual: #514045;
    --bg-yellow: #4D4C43;
    --bg-green: #425047;
    --bg-blue: #3A515D;
    --gray-0: #7A8478;
    --gray-1: #859289;
    --gray-2: #9DA9A0;
}

/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--bg-0);
    color: var(--foreground);
    line-height: 1.6;
    min-height: 100vh;
    transition: background-color 0.3s ease, color 0.3s ease;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Desktop Background Enhancement */
@media (min-width: 769px) {
    body {
        background: linear-gradient(135deg, var(--bg-0) 0%, var(--bg-1) 100%);
    }
}

/* Theme Toggle Button */
.theme-toggle {
    position: fixed;
    top: 1rem;
    right: 1rem;
    z-index: 1000;
    background: var(--bg-2);
    border: 2px solid var(--bg-4);
    border-radius: 50%;
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 1.5rem;
}

.theme-toggle:hover {
    background: var(--bg-3);
    transform: scale(1.05);
}

/* Install Button (PWA) */
.install-btn {
    position: fixed;
    top: 1rem;
    left: 1rem;
    z-index: 1000;
    background: var(--green);
    color: var(--bg-0);
    border: none;
    border-radius: 12px;
    padding: 0.75rem 1.25rem;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.install-btn:hover {
    background: var(--aqua);
    transform: translateY(-2px);
    box-shadow: 0 6px 16px rgba(0, 0, 0, 0.25);
}

.install-btn.hidden {
    display: none;
}

/* Container */

.theme-toggle:active {
    transform: scale(0.95);
}

/* Screen Management */
.screen {
    display: none;
    min-height: 100vh;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.screen.active {
    display: block;
    opacity: 1;
}

.container {
    max-width: 600px;
    margin: 0 auto;
    padding: 2rem 1rem;
}

/* Desktop layout improvements */
@media (min-width: 769px) {
    .container {
        max-width: 900px;
        padding: 3rem 2rem;
    }
}

/* Home Screen */
.app-title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--green);
    text-align: center;
    margin-top: 2rem;
    margin-bottom: 0.5rem;
}

@media (min-width: 769px) {
    .app-title {
        font-size: 3rem;
        margin-top: 3rem;
    }
}

.app-subtitle {
    text-align: center;
    color: var(--gray-1);
    margin-bottom: 3rem;
    font-size: 1rem;
}

@media (min-width: 769px) {
    .app-subtitle {
        font-size: 1.25rem;
        margin-bottom: 4rem;
    }
}

.menu-buttons {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

/* Desktop grid layout for menu buttons */
@media (min-width: 769px) {
    .menu-buttons {
        display: grid;
        grid-template-columns: repeat(2, 1fr);
        gap: 1.5rem;
    }
}

.menu-btn {
    background: var(--bg-1);
    border: 2px solid var(--bg-3);
    border-radius: 16px;
    padding: 1.5rem;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    text-align: left;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
    position: relative;
    overflow: hidden;
}

.menu-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, transparent 0%, var(--bg-2) 100%);
    opacity: 0;
    transition: opacity 0.3s ease;
}

.menu-btn:hover {
    background: var(--bg-2);
    border-color: var(--green);
    transform: translateY(-4px);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.15);
}

.menu-btn:hover::before {
    opacity: 1;
}

.menu-btn:active {
    transform: translateY(-2px);
}

.menu-btn > * {
    position: relative;
    z-index: 1;
}

.btn-icon {
    font-size: 2rem;
    margin-bottom: 0.5rem;
}

.btn-text {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--foreground);
}

.btn-desc {
    font-size: 0.9rem;
    color: var(--gray-1);
}

/* Quiz Screen */
.quiz-header {
    background: var(--bg-1);
    border-bottom: 2px solid var(--bg-3);
    padding: 1rem;
    display: flex;
    align-items: center;
    gap: 1rem;
    position: sticky;
    top: 0;
    z-index: 100;
}

.icon-btn {
    background: transparent;
    border: none;
    font-size: 1.5rem;
    color: var(--foreground);
    cursor: pointer;
    padding: 0.5rem;
    transition: all 0.2s ease;
}

.icon-btn:hover {
    color: var(--green);
    transform: scale(1.1);
}

.quiz-info {
    flex: 1;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-weight: 500;
}

#question-counter.interactive {
    cursor: pointer;
    text-decoration: underline;
    text-decoration-style: dashed;
    text-underline-offset: 4px;
    transition: color 0.2s ease;
}

#question-counter.interactive:hover {
    color: var(--blue);
}

#jump-input {
    width: 60px;
    padding: 2px 4px;
    border: 2px solid var(--blue);
    border-radius: 6px;
    font-size: 1rem;
    font-weight: 600;
    text-align: center;
    font-family: inherit;
    color: var(--foreground);
    background: var(--bg-0);
}

.timer {
    color: var(--blue);
    font-variant-numeric: tabular-nums;
    font-weight: 600;
    transition: color 0.3s ease;
}

.timer-warning {
    color: var(--red) !important;
}

.timer-critical {
    color: var(--red) !important;
    animation: pulse 1s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% {
        opacity: 1;
        transform: scale(1);
    }
    50% {
        opacity: 0.7;
        transform: scale(1.05);
    }
}

.quiz-container {
    max-width: 700px;
    margin: 0 auto;
    padding: 2rem 1.5rem;
}

@media (min-width: 769px) {
    .quiz-container {
        background: var(--bg-1);
        border-radius: 16px;
        margin-top: 2rem;
        margin-bottom: 2rem;
        padding: 2.5rem;
        box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    }
}

.question-section {
    margin-bottom: 2rem;
}

.question-image {
    margin-bottom: 1.5rem;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.question-image img {
    margin: auto;
    max-width: 100%;
    height: auto;
    display: block;
}

@media (min-width: 769px) {
    .question-image {
        max-width: 500px;
        margin-left: auto;
        margin-right: auto;
    }
}

.question-text {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    line-height: 1.5;
}

.question-text:empty {
    display: none;
    margin: 0;
}

.choices-container {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.choice-btn {
    background: var(--bg-1);
    border: 2px solid var(--bg-3);
    border-radius: 12px;
    padding: 1.25rem;
    text-align: left;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    font-size: 1.05rem;
    color: var(--foreground);
    line-height: 1.5;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.06);
}

.choice-btn:hover:not(:disabled) {
    background: var(--bg-2);
    border-color: var(--blue);
    transform: translateX(4px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.12);
}

.choice-btn:disabled {
    cursor: not-allowed;
}

.choice-btn.selected {
    border-color: var(--blue);
    background: var(--bg-blue);
}

.choice-btn.correct {
    border-color: var(--green);
    background: var(--bg-green);
}

.choice-btn.incorrect {
    border-color: var(--red);
    background: var(--bg-red);
}

/* Feedback */
.feedback {
    margin-top: 2rem;
    padding: 1.5rem;
    border-radius: 8px;
    text-align: center;
}

.feedback.hidden {
    display: none;
}

.feedback.correct {
    background: var(--bg-green);
    color: var(--green);
}

.feedback.incorrect {
    background: var(--bg-red);
    color: var(--red);
}

#feedback-text {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1rem;
}

.next-btn {
    background: var(--green);
    color: var(--bg-0);
    border: none;
    border-radius: 8px;
    padding: 0.75rem 2rem;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}

.next-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.next-btn:active {
    transform: translateY(0);
}

.next-btn.hidden {
    display: none;
}

/* Skip Button */
.skip-btn {
    display: block;
    width: 100%;
    margin-top: 1.5rem;
    background: transparent;
    color: var(--gray-1);
    border: 2px dashed var(--bg-3);
    border-radius: 8px;
    padding: 0.75rem 1.5rem;
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
}

.skip-btn:hover {
    background: var(--bg-1);
    border-color: var(--gray-1);
    color: var(--foreground);
}

.skip-btn:active {
    transform: scale(0.98);
}

.skip-btn.hidden {
    display: none;
}

/* Stats Screen */
.stats-header {
    background: var(--bg-1);
    border-bottom: 2px solid var(--bg-3);
    padding: 1rem;
    display: flex;
    align-items: center;
    gap: 1rem;
    position: sticky;
    top: 0;
    z-index: 100;
}

.stats-header h2 {
    flex: 1;
    font-size: 1.5rem;
}

.stats-container {
    max-width: 800px;
    margin: 0 auto;
    padding: 1.5rem;
}

.stats-summary {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
}

.stat-card {
    background: var(--bg-1);
    border: 2px solid var(--bg-3);
    border-radius: 8px;
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
}

.stat-value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--green);
}

.stat-label {
    font-size: 0.9rem;
    color: var(--gray-1);
}

.legend {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    margin-bottom: 1.5rem;
    justify-content: center;
}

.legend-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
}

.legend-color {
    width: 20px;
    height: 20px;
    border-radius: 4px;
    border: 1px solid var(--bg-4);
}

.questions-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(50px, 1fr));
    gap: 0.5rem;
}

.question-cell {
    aspect-ratio: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 6px;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    border: 2px solid transparent;
}

.question-cell:hover {
    transform: scale(1.1);
    border-color: var(--foreground);
    z-index: 10;
}

.question-cell.not-seen {
    background: var(--gray-0);
    color: var(--bg-0);
}

.question-cell.struggling {
    background: var(--red);
    color: var(--bg-0);
}

.question-cell.learning {
    background: var(--yellow);
    color: var(--bg-0);
}

.question-cell.mastered {
    background: var(--green);
    color: var(--bg-0);
}

/* Question Detail Modal */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.6);
    backdrop-filter: blur(4px);
    z-index: 2000;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 1rem;
    opacity: 0;
    transition: opacity 0.3s ease;
}

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

.modal-overlay.visible {
    opacity: 1;
}

.modal-content {
    background: var(--bg-1);
    border: 2px solid var(--bg-4);
    border-radius: 16px;
    padding: 2rem;
    max-width: 600px;
    width: 100%;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
    transform: scale(0.9);
    transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.modal-overlay.visible .modal-content {
    transform: scale(1);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
    padding-bottom: 1rem;
    border-bottom: 2px solid var(--bg-3);
}

.modal-header h3 {
    font-size: 1.5rem;
    color: var(--green);
    margin: 0;
}

.modal-close {
    background: transparent;
    border: none;
    font-size: 1.5rem;
    color: var(--foreground);
    cursor: pointer;
    padding: 0.5rem;
    line-height: 1;
    transition: all 0.2s ease;
    border-radius: 8px;
}

.modal-close:hover {
    background: var(--bg-2);
    color: var(--red);
}

.modal-image {
    margin-bottom: 1.5rem;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.modal-image img {
    width: 100%;
    height: auto;
    display: block;
}

.modal-question {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--foreground);
}

.modal-choices {
    margin-bottom: 1.5rem;
}

.modal-choice {
    padding: 0.75rem;
    margin-bottom: 0.5rem;
    border-radius: 8px;
    background: var(--bg-2);
    border: 2px solid transparent;
    line-height: 1.5;
}

.modal-choice.correct {
    background: var(--bg-green);
    border-color: var(--green);
    font-weight: 600;
}

.modal-stats {
    padding: 1rem;
    background: var(--bg-2);
    border-radius: 8px;
    font-size: 0.95rem;
}

.modal-stats-row {
    display: flex;
    justify-content: space-between;
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--bg-3);
}

.modal-stats-row:last-child {
    border-bottom: none;
}

.modal-stats-label {
    color: var(--gray-1);
}

.modal-stats-value {
    font-weight: 600;
    color: var(--foreground);
}

/* Mobile Optimizations */
@media (max-width: 768px) {
    .app-title {
        font-size: 1.75rem;
    }

    .questions-grid {
        grid-template-columns: repeat(auto-fill, minmax(45px, 1fr));
        gap: 0.4rem;
    }

    .modal-content {
        padding: 1.5rem;
        max-height: 95vh;
    }

    .modal-header h3 {
        font-size: 1.25rem;
    }
}

/* Loading State */
.loading {
    text-align: center;
    padding: 2rem;
    color: var(--gray-1);
}

/* Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.choice-btn {
    animation: fadeIn 0.3s ease forwards;
}

.choice-btn:nth-child(1) { animation-delay: 0.05s; }
.choice-btn:nth-child(2) { animation-delay: 0.1s; }
.choice-btn:nth-child(3) { animation-delay: 0.15s; }
.choice-btn:nth-child(4) { animation-delay: 0.2s; }