/* ===================================
   CSS CUSTOM PROPERTIES (VARIABLES)
   =================================== */
:root {
    /* Color Palette */
    --color-primary: #6366f1;
    --color-primary-dark: #4f46e5;
    --color-primary-light: #818cf8;
    --color-success: #10b981;
    --color-error: #ef4444;
    --color-warning: #f59e0b;
    --color-neutral-100: #f3f4f6;
    --color-neutral-200: #e5e7eb;
    --color-neutral-300: #d1d5db;
    --color-neutral-700: #374151;
    --color-neutral-800: #1f2937;
    --color-neutral-900: #111827;
    --color-white: #ffffff;

    /* Typography */
    --font-family-base: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 2rem;
    --font-weight-normal: 400;
    --font-weight-medium: 500;
    --font-weight-semibold: 600;
    --font-weight-bold: 700;

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 0.75rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;

    /* 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), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);

    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-base: 250ms ease-in-out;
    --transition-slow: 350ms ease-in-out;
}

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

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-family-base);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--color-neutral-800);
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: var(--spacing-md);
}

/* ===================================
   LAYOUT
   =================================== */
.container {
    max-width: 900px;
    margin: 0 auto;
    background-color: var(--color-white);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-xl);
    overflow: hidden;
    min-height: calc(100vh - 2rem);
    display: flex;
    flex-direction: column;
}

/* ===================================
   HEADER
   =================================== */
.header {
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    color: var(--color-white);
    padding: var(--spacing-xl);
    text-align: center;
    position: relative;
}

.header__title {
    font-size: var(--font-size-3xl);
    font-weight: var(--font-weight-bold);
    margin-bottom: var(--spacing-xs);
}

.header__subtitle {
    font-size: var(--font-size-lg);
    opacity: 0.9;
    font-weight: var(--font-weight-normal);
}

.back-link {
    position: absolute;
    top: var(--spacing-lg);
    left: var(--spacing-lg);
    color: var(--color-white);
    text-decoration: none;
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-medium);
    transition: opacity var(--transition-fast);
}

.back-link:hover {
    opacity: 0.8;
}

/* Progress Bar */
.progress-bar {
    width: 100%;
    height: 8px;
    background-color: rgba(255, 255, 255, 0.3);
    border-radius: var(--radius-sm);
    overflow: hidden;
    margin-top: var(--spacing-lg);
}

.progress-bar__fill {
    height: 100%;
    background-color: var(--color-white);
    transition: width var(--transition-slow);
    border-radius: var(--radius-sm);
}

.progress-text {
    margin-top: var(--spacing-sm);
    font-size: var(--font-size-sm);
    opacity: 0.9;
}

/* ===================================
   MAIN CONTENT
   =================================== */
.main {
    flex: 1;
    padding: var(--spacing-xl);
}

/* ===================================
   QUIZ GRID (INDEX PAGE)
   =================================== */
.quiz-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--spacing-lg);
}

.quiz-card {
    background-color: var(--color-white);
    border: 2px solid var(--color-neutral-200);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    cursor: pointer;
    transition: all var(--transition-base);
    text-decoration: none;
    color: inherit;
    display: block;
}

.quiz-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--color-primary);
}

.quiz-card__icon {
    font-size: var(--font-size-3xl);
    margin-bottom: var(--spacing-md);
}

.quiz-card__title {
    font-size: var(--font-size-xl);
    font-weight: var(--font-weight-semibold);
    margin-bottom: var(--spacing-sm);
    color: var(--color-neutral-900);
}

.quiz-card__description {
    font-size: var(--font-size-sm);
    color: var(--color-neutral-700);
    margin-bottom: var(--spacing-md);
    line-height: 1.5;
}

.quiz-card__meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: var(--font-size-xs);
    color: var(--color-neutral-700);
}

.quiz-card__difficulty {
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-sm);
    font-weight: var(--font-weight-medium);
}

.quiz-card__difficulty--easy {
    background-color: #d1fae5;
    color: #065f46;
}

.quiz-card__difficulty--medium {
    background-color: #fef3c7;
    color: #92400e;
}

.quiz-card__difficulty--hard {
    background-color: #fee2e2;
    color: #991b1b;
}

/* Random Party Card - Special styling */
.quiz-card--random {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    border-color: #667eea;
    color: var(--color-white);
    position: relative;
    overflow: hidden;
}

.quiz-card--random::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(255,255,255,0.1) 0%, transparent 70%);
    animation: rotate 20s linear infinite;
}

.quiz-card--random:hover {
    transform: translateY(-4px) scale(1.02);
    box-shadow: 0 20px 40px rgba(102, 126, 234, 0.4);
    border-color: #667eea;
}

.quiz-card--random .quiz-card__title,
.quiz-card--random .quiz-card__description,
.quiz-card--random .quiz-card__meta {
    color: var(--color-white);
    position: relative;
    z-index: 1;
}

.quiz-card--random .quiz-card__difficulty {
    background-color: rgba(255, 255, 255, 0.3);
    color: var(--color-white);
}

@keyframes rotate {
    from {
        transform: rotate(0deg);
    }
    to {
        transform: rotate(360deg);
    }
}

/* ===================================
   QUIZ CONTAINER (QUIZ PAGE)
   =================================== */
.quiz-container {
    max-width: 700px;
    margin: 0 auto;
}

.question-card {
    background-color: var(--color-white);
    border: 2px solid var(--color-neutral-200);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    margin-bottom: var(--spacing-lg);
}

.question-card__number {
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-semibold);
    color: var(--color-primary);
    margin-bottom: var(--spacing-sm);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.question-card__text {
    font-size: var(--font-size-xl);
    font-weight: var(--font-weight-semibold);
    color: var(--color-neutral-900);
    margin-bottom: var(--spacing-xl);
    line-height: 1.4;
}

.options-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.option-item {
    position: relative;
}

.option-button {
    width: 100%;
    text-align: left;
    padding: var(--spacing-lg);
    border: 2px solid var(--color-neutral-300);
    background-color: var(--color-white);
    border-radius: var(--radius-md);
    font-size: var(--font-size-base);
    font-family: inherit;
    cursor: pointer;
    transition: all var(--transition-fast);
    font-weight: var(--font-weight-medium);
    color: var(--color-neutral-800);
}

.option-button:hover:not(:disabled) {
    border-color: var(--color-primary);
    background-color: var(--color-neutral-100);
    transform: translateX(4px);
}

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

.option-button.selected {
    border-color: var(--color-primary);
    background-color: var(--color-primary-light);
    color: var(--color-white);
}

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

.option-button.incorrect {
    border-color: var(--color-error);
    background-color: var(--color-error);
    color: var(--color-white);
}

.option-button.dimmed {
    opacity: 0.5;
}

/* Feedback Message */
.feedback {
    margin-top: var(--spacing-lg);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-medium);
    animation: slideIn var(--transition-base);
}

.feedback--correct {
    background-color: #d1fae5;
    color: #065f46;
    border: 2px solid var(--color-success);
}

.feedback--incorrect {
    background-color: #fee2e2;
    color: #991b1b;
    border: 2px solid var(--color-error);
}

.feedback__title {
    font-weight: var(--font-weight-bold);
    margin-bottom: var(--spacing-xs);
}

.feedback__explanation {
    font-size: var(--font-size-sm);
    opacity: 0.9;
}

/* Navigation Buttons */
.navigation {
    display: flex;
    justify-content: flex-end;
    margin-top: var(--spacing-xl);
}

/* ===================================
   RESULTS CONTAINER
   =================================== */
.results-container {
    max-width: 600px;
    margin: 0 auto;
}

.results-card {
    background-color: var(--color-white);
    border: 2px solid var(--color-neutral-200);
    border-radius: var(--radius-lg);
    padding: var(--spacing-2xl);
    text-align: center;
    animation: scaleIn var(--transition-slow);
}

.results__title {
    font-size: var(--font-size-3xl);
    font-weight: var(--font-weight-bold);
    color: var(--color-neutral-900);
    margin-bottom: var(--spacing-xl);
}

.results__score {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-xl);
    padding: var(--spacing-xl);
    background: linear-gradient(135deg, var(--color-primary-light) 0%, var(--color-primary) 100%);
    border-radius: var(--radius-lg);
    color: var(--color-white);
}

.score-label {
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-medium);
    opacity: 0.9;
}

.score-value {
    font-size: 4rem;
    font-weight: var(--font-weight-bold);
    line-height: 1;
}

.score-percentage {
    font-size: var(--font-size-xl);
    font-weight: var(--font-weight-semibold);
}

.results__message {
    font-size: var(--font-size-lg);
    color: var(--color-neutral-700);
    margin-bottom: var(--spacing-xl);
    line-height: 1.6;
}

.results__actions {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* ===================================
   BUTTONS
   =================================== */
.btn {
    padding: var(--spacing-md) var(--spacing-xl);
    border: none;
    border-radius: var(--radius-md);
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-semibold);
    font-family: inherit;
    cursor: pointer;
    transition: all var(--transition-fast);
    text-decoration: none;
    display: inline-block;
    text-align: center;
}

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

.btn--primary:hover {
    background-color: var(--color-primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn--secondary {
    background-color: var(--color-neutral-200);
    color: var(--color-neutral-800);
}

.btn--secondary:hover {
    background-color: var(--color-neutral-300);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

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

/* ===================================
   FOOTER
   =================================== */
.footer {
    padding: var(--spacing-lg);
    text-align: center;
    font-size: var(--font-size-sm);
    color: var(--color-neutral-700);
    background-color: var(--color-neutral-100);
    border-top: 1px solid var(--color-neutral-200);
}

/* ===================================
   UTILITY CLASSES
   =================================== */
.loading {
    text-align: center;
    padding: var(--spacing-2xl);
    color: var(--color-neutral-700);
    font-size: var(--font-size-lg);
}

.error {
    text-align: center;
    padding: var(--spacing-xl);
    color: var(--color-error);
    background-color: #fee2e2;
    border-radius: var(--radius-md);
    font-weight: var(--font-weight-medium);
}

/* ===================================
   ANIMATIONS
   =================================== */
@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes scaleIn {
    from {
        opacity: 0;
        transform: scale(0.95);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

/* ===================================
   RESPONSIVE DESIGN
   =================================== */
@media (max-width: 640px) {
    :root {
        --font-size-3xl: 1.75rem;
        --font-size-2xl: 1.375rem;
    }

    body {
        padding: 0;
    }

    .container {
        border-radius: 0;
        min-height: 100vh;
    }

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

    .main {
        padding: var(--spacing-lg);
    }

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

    .question-card {
        padding: var(--spacing-lg);
    }

    .results-card {
        padding: var(--spacing-xl);
    }

    .score-value {
        font-size: 3rem;
    }

    .results__actions {
        flex-direction: column;
        width: 100%;
    }

    .btn {
        width: 100%;
    }
}

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}