/* ===== CSS Variables ===== */
:root {
    /* Colors - Light Theme */
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;

    --success: #10b981;
    --error: #ef4444;
    --warning: #f59e0b;

    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;

    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-tertiary: #94a3b8;

    --border-color: #e2e8f0;
    --border-hover: #cbd5e1;

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 0.75rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;

    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;

    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);

    /* Transitions */
    --transition: 0.2s ease;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg-secondary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
    min-height: 100vh;
}

/* ===== Container ===== */
.container {
    max-width: 900px;
    margin: 0 auto;
    padding: var(--spacing-md);
}

/* ===== Header ===== */
.header {
    margin-bottom: var(--spacing-lg);
}

.header-content {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: var(--spacing-md);
    box-shadow: var(--shadow-sm);
    flex-wrap: wrap;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.logo-icon {
    width: 40px;
    height: 40px;
    background: var(--primary);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.logo-icon svg {
    width: 24px;
    height: 24px;
    color: white;
}

.logo-text h1 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.125rem;
}

.logo-text p {
    font-size: 0.75rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.header-stats {
    display: flex;
    gap: var(--spacing-sm);
}

.stat-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-sm);
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    min-width: 80px;
    transition: all var(--transition);
}

.stat-card:hover {
    border-color: var(--border-hover);
    transform: translateY(-1px);
}

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

.stat-info {
    display: flex;
    flex-direction: column;
}

.stat-label {
    font-size: 0.625rem;
    color: var(--text-tertiary);
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.025em;
}

.stat-value {
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-primary);
}

/* ===== Welcome Screen ===== */
.welcome-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    text-align: center;
    box-shadow: var(--shadow-md);
    max-width: 550px;
    margin: 0 auto;
}

.welcome-icon {
    width: 64px;
    height: 64px;
    background: var(--primary);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto var(--spacing-md);
}

.welcome-icon svg {
    width: 32px;
    height: 32px;
    color: white;
}

.welcome-card h2 {
    font-size: 1.75rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.welcome-card>p {
    color: var(--text-secondary);
    font-size: 1rem;
    margin-bottom: var(--spacing-lg);
    line-height: 1.5;
}

/* ===== Topic Selection ===== */
.topic-selection {
    margin: var(--spacing-lg) 0;
    text-align: left;
}

.topic-selection h3 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

.topic-grid {
    display: grid;
    gap: var(--spacing-sm);
}

.topic-checkbox {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md);
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition);
    position: relative;
}

.topic-checkbox:hover {
    border-color: var(--primary);
    background: var(--bg-primary);
}

.topic-checkbox input[type="checkbox"] {
    position: absolute;
    opacity: 0;
    cursor: pointer;
}

.checkbox-custom {
    width: 20px;
    height: 20px;
    border: 2px solid var(--border-color);
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition);
    flex-shrink: 0;
}

.topic-checkbox input[type="checkbox"]:checked~.checkbox-custom {
    background: var(--primary);
    border-color: var(--primary);
}

.topic-checkbox input[type="checkbox"]:checked~.checkbox-custom::after {
    content: '✓';
    color: white;
    font-weight: bold;
    font-size: 12px;
}

.topic-name {
    flex: 1;
    font-weight: 600;
    font-size: 0.875rem;
    color: var(--text-primary);
}

.topic-count {
    font-size: 0.75rem;
    color: var(--text-tertiary);
    background: var(--bg-tertiary);
    padding: 0.25rem 0.625rem;
    border-radius: 999px;
}

/* ===== Buttons ===== */
.btn-primary,
.btn-secondary {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    font-weight: 600;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    transition: all var(--transition);
    font-family: inherit;
}

.btn-primary {
    background: var(--primary);
    color: white;
    box-shadow: var(--shadow-sm);
}

.btn-primary:hover:not(:disabled) {
    background: var(--primary-dark);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-primary:active:not(:disabled) {
    transform: translateY(0);
}

.btn-primary:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn-primary svg,
.btn-secondary svg {
    width: 18px;
    height: 18px;
}

.btn-secondary {
    background: var(--bg-secondary);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover:not(:disabled) {
    background: var(--bg-primary);
    border-color: var(--border-hover);
}

.btn-secondary:disabled {
    opacity: 0.3;
    cursor: not-allowed;
}

/* ===== Progress Bar ===== */
.progress-container {
    margin-bottom: var(--spacing-lg);
}

.progress-info {
    display: flex;
    justify-content: space-between;
    margin-bottom: var(--spacing-xs);
    font-size: 0.75rem;
    font-weight: 600;
}

.progress-text {
    color: var(--text-secondary);
}

.progress-percentage {
    color: var(--primary);
}

.progress-bar {
    height: 6px;
    background: var(--bg-tertiary);
    border-radius: 999px;
    overflow: hidden;
    border: 1px solid var(--border-color);
}

.progress-fill {
    height: 100%;
    background: var(--primary);
    border-radius: 999px;
    transition: width var(--transition);
}

/* ===== Question Card ===== */
.question-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-md);
}

.question-header {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
    flex-wrap: wrap;
}

.question-topic {
    background: var(--primary);
    color: white;
    padding: 0.375rem 0.75rem;
    border-radius: 999px;
    font-size: 0.75rem;
    font-weight: 600;
}

.question-difficulty {
    background: var(--bg-secondary);
    color: var(--text-secondary);
    padding: 0.375rem 0.75rem;
    border-radius: 999px;
    font-size: 0.75rem;
    font-weight: 600;
    border: 1px solid var(--border-color);
}

.question-content {
    margin-bottom: var(--spacing-md);
}

.question-text {
    font-size: 1rem;
    font-weight: 600;
    line-height: 1.5;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

/* ===== Code Block ===== */
.code-block {
    background: #282c34;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    overflow: hidden;
    margin-top: var(--spacing-md);
}

.code-header {
    background: rgba(0, 0, 0, 0.2);
    padding: var(--spacing-sm);
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.code-language {
    font-size: 0.625rem;
    font-weight: 600;
    color: #abb2bf;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.code-copy {
    background: none;
    border: none;
    color: #abb2bf;
    cursor: pointer;
    padding: 0.25rem;
    display: flex;
    align-items: center;
    transition: color var(--transition);
}

.code-copy:hover {
    color: #61afef;
}

.code-copy svg {
    width: 14px;
    height: 14px;
}

.code-block pre {
    margin: 0;
    padding: var(--spacing-md);
    overflow-x: auto;
    background: #282c34;
}

.code-block code {
    font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
    font-size: 0.8125rem;
    line-height: 1.5;
    color: #abb2bf;
}

/* Highlight.js override */
.code-block .hljs {
    background: #282c34;
    padding: 0;
}

/* ===== Hint Card ===== */
.hint-card {
    margin-top: var(--spacing-md);
}

.hint-toggle {
    width: 100%;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-sm);
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    cursor: pointer;
    transition: all var(--transition);
    font-family: inherit;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.hint-toggle:hover {
    background: var(--bg-primary);
    border-color: var(--primary);
    color: var(--primary);
}

.hint-toggle svg {
    width: 18px;
    height: 18px;
}

.hint-content {
    margin-top: var(--spacing-sm);
    padding: var(--spacing-md);
    background: rgba(99, 102, 241, 0.05);
    border: 1px solid rgba(99, 102, 241, 0.2);
    border-radius: var(--radius-md);
    animation: slideDown 0.3s ease;
}

.hint-content p {
    font-size: 0.875rem;
    color: var(--text-secondary);
    line-height: 1.5;
    margin: 0;
}

/* ===== Options ===== */
.options-container {
    display: grid;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.option {
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    cursor: pointer;
    transition: all var(--transition);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.option:hover:not(.disabled) {
    background: var(--bg-primary);
    border-color: var(--primary);
    transform: translateX(2px);
}

.option-letter {
    width: 32px;
    height: 32px;
    background: var(--bg-tertiary);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 0.75rem;
    flex-shrink: 0;
    transition: all var(--transition);
    color: var(--text-secondary);
}

.option-text {
    flex: 1;
    font-size: 0.875rem;
    line-height: 1.4;
    color: var(--text-primary);
}

.option.selected {
    background: rgba(99, 102, 241, 0.05);
    border-color: var(--primary);
}

.option.selected .option-letter {
    background: var(--primary);
    color: white;
}

.option.correct {
    background: rgba(16, 185, 129, 0.05);
    border-color: var(--success);
}

.option.correct .option-letter {
    background: var(--success);
    color: white;
}

.option.wrong {
    background: rgba(239, 68, 68, 0.05);
    border-color: var(--error);
}

.option.wrong .option-letter {
    background: var(--error);
    color: white;
}

.option.disabled {
    cursor: not-allowed;
}

/* ===== Question Footer ===== */
.question-footer {
    display: flex;
    justify-content: space-between;
    gap: var(--spacing-sm);
}

/* ===== Feedback Area (Sabit) ===== */
.feedback-area {
    margin-top: var(--spacing-md);
    margin-bottom: var(--spacing-md);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    border: 2px solid;
    animation: slideDown 0.3s ease;
}

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

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.feedback-area.correct {
    background: rgba(16, 185, 129, 0.05);
    border-color: var(--success);
}

.feedback-area.wrong {
    background: rgba(239, 68, 68, 0.05);
    border-color: var(--error);
}

.feedback-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-xs);
}

.feedback-area .feedback-icon {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1rem;
    font-weight: bold;
    flex-shrink: 0;
}

.feedback-area.correct .feedback-icon {
    background: var(--success);
    color: white;
}

.feedback-area.wrong .feedback-icon {
    background: var(--error);
    color: white;
}

.feedback-area h4 {
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-primary);
    margin: 0;
}

.feedback-area p {
    font-size: 0.875rem;
    color: var(--text-secondary);
    line-height: 1.5;
    margin: 0;
}


/* ===== Results Screen ===== */
.results-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    text-align: center;
    box-shadow: var(--shadow-md);
    max-width: 600px;
    margin: 0 auto;
}

.results-icon {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto var(--spacing-lg);
}

.results-icon.success {
    background: var(--success);
}

.results-icon.fail {
    background: var(--error);
}

.results-icon svg {
    width: 40px;
    height: 40px;
    color: white;
}

.results-card h2 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.results-card>p {
    color: var(--text-secondary);
    font-size: 1rem;
    margin-bottom: var(--spacing-xl);
}

.results-stats {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-xl);
}

.result-stat {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
}

.result-stat-value {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--primary);
    margin-bottom: 0.25rem;
}

.result-stat-label {
    font-size: 0.75rem;
    color: var(--text-secondary);
    font-weight: 600;
}

.results-actions {
    display: flex;
    justify-content: center;
    gap: var(--spacing-sm);
}

/* ===== Utility Classes ===== */
.hidden {
    display: none !important;
}

.background-animation {
    display: none;
}

/* ===== Responsive Design ===== */
@media (max-width: 768px) {
    .container {
        padding: var(--spacing-sm);
    }

    .header {
        margin-bottom: var(--spacing-md);
    }

    .header-content {
        padding: var(--spacing-sm);
    }

    .logo-icon {
        width: 36px;
        height: 36px;
    }

    .logo-icon svg {
        width: 20px;
        height: 20px;
    }

    .logo-text h1 {
        font-size: 1.125rem;
    }

    .logo-text p {
        font-size: 0.6875rem;
    }

    .header-stats {
        width: 100%;
        justify-content: space-between;
    }

    .stat-card {
        flex: 1;
        min-width: 0;
        padding: 0.5rem;
    }

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

    .stat-label {
        font-size: 0.5625rem;
    }

    .stat-value {
        font-size: 0.875rem;
    }

    .welcome-card,
    .question-card,
    .results-card {
        padding: var(--spacing-md);
    }

    .welcome-icon {
        width: 56px;
        height: 56px;
    }

    .welcome-icon svg {
        width: 28px;
        height: 28px;
    }

    .welcome-card h2 {
        font-size: 1.5rem;
    }

    .welcome-card>p {
        font-size: 0.875rem;
    }

    .topic-selection h3 {
        font-size: 0.875rem;
    }

    .topic-checkbox {
        padding: var(--spacing-sm);
    }

    .question-text {
        font-size: 0.9375rem;
    }

    .question-footer {
        flex-direction: column;
    }

    .btn-primary,
    .btn-secondary {
        width: 100%;
        justify-content: center;
        padding: 0.625rem 1.25rem;
        font-size: 0.8125rem;
    }

    .feedback-toast {
        left: var(--spacing-sm);
        right: var(--spacing-sm);
        bottom: var(--spacing-sm);
        padding: var(--spacing-sm);
    }

    .feedback-icon {
        width: 36px;
        height: 36px;
        font-size: 1.125rem;
    }

    .feedback-content h4 {
        font-size: 0.8125rem;
    }

    .feedback-content p {
        font-size: 0.6875rem;
    }

    .results-card h2 {
        font-size: 1.5rem;
    }

    .results-icon {
        width: 64px;
        height: 64px;
    }

    .results-icon svg {
        width: 32px;
        height: 32px;
    }

    .results-stats {
        grid-template-columns: repeat(2, 1fr);
        gap: var(--spacing-sm);
    }

    .result-stat {
        padding: var(--spacing-sm);
    }

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

    .code-block pre {
        font-size: 0.75rem;
        padding: var(--spacing-sm);
    }

    .code-block code {
        font-size: 0.75rem;
    }

    .option {
        padding: var(--spacing-sm);
    }

    .option-letter {
        width: 28px;
        height: 28px;
        font-size: 0.6875rem;
    }

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

@media (max-width: 480px) {
    .logo-text h1 {
        font-size: 1rem;
    }

    .welcome-card h2 {
        font-size: 1.25rem;
    }

    .question-text {
        font-size: 0.875rem;
    }

    .results-card h2 {
        font-size: 1.25rem;
    }

    .result-stat-value {
        font-size: 1.25rem;
    }
}