/* ===========================
   CSS Custom Properties
   =========================== */
:root {
    --marvel-red: #ed1d24;
    --marvel-dark: #202020;
    --marvel-darker: #151515;
    --marvel-light: #f5f5f5;
    --success-green: #28a745;
    --error-red: #dc3545;
    --transition-speed: 0.3s;
    --card-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
    --card-shadow-hover: 0 15px 40px rgba(0, 0, 0, 0.4);
}

/* ===========================
   Global Styles
   =========================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    background: linear-gradient(135deg, var(--marvel-darker) 0%, var(--marvel-dark) 100%);
    color: var(--marvel-light);
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    min-height: 100vh;
    line-height: 1.6;
}

/* ===========================
   Typography
   =========================== */
h1, h2, h3 {
    font-weight: 700;
    letter-spacing: -0.5px;
}

.display-4 {
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
}

/* ===========================
   Header Styles
   =========================== */
header {
    background: linear-gradient(to right, var(--marvel-darker), var(--marvel-dark));
    border-bottom: 3px solid var(--marvel-red);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

/* ===========================
   Card Styles
   =========================== */
.quiz-card {
    background: rgba(255, 255, 255, 0.05);
    backdrop-filter: blur(10px);
    border-radius: 20px;
    box-shadow: var(--card-shadow);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: all var(--transition-speed) ease;
    animation: fadeInUp 0.5s ease;
}

.quiz-card:hover {
    box-shadow: var(--card-shadow-hover);
    transform: translateY(-2px);
}

.card-body {
    background: linear-gradient(145deg, rgba(255, 255, 255, 0.08), rgba(255, 255, 255, 0.02));
    border-radius: 20px;
}

/* ===========================
   Progress Bar
   =========================== */
.quiz-progress {
    padding: 15px;
    background: rgba(255, 255, 255, 0.05);
    border-radius: 15px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.progress {
    background: rgba(255, 255, 255, 0.1);
    border-radius: 10px;
    overflow: hidden;
}

.progress-bar {
    transition: width 0.5s ease;
    background: linear-gradient(90deg, var(--marvel-red), #ff4757);
}

/* ===========================
   Question Styles
   =========================== */
.question-text {
    font-size: 1.5rem;
    font-weight: 600;
    color: #fff;
    text-align: center;
    line-height: 1.4;
}

#character-image {
    max-width: 100%;
    margin: 0 auto;
}

#character-image img {
    max-width: 300px;
    width: 100%;
    height: auto;
    border-radius: 15px;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.4);
    border: 3px solid rgba(255, 255, 255, 0.1);
    transition: transform var(--transition-speed) ease;
}

#character-image img:hover {
    transform: scale(1.05);
}

/* ===========================
   Answer Buttons
   =========================== */
.answers-container {
    display: grid;
    grid-template-columns: 1fr;
    gap: 15px;
}

.answer-btn {
    width: 100%;
    padding: 18px 24px;
    background: linear-gradient(145deg, rgba(255, 255, 255, 0.1), rgba(255, 255, 255, 0.05));
    color: #fff;
    border: 2px solid rgba(255, 255, 255, 0.2);
    border-radius: 12px;
    font-size: 1.1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-speed) ease;
    text-align: left;
    position: relative;
    overflow: hidden;
}

.answer-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.1), transparent);
    transition: left 0.5s ease;
}

.answer-btn:hover {
    background: linear-gradient(145deg, rgba(237, 29, 36, 0.3), rgba(237, 29, 36, 0.2));
    border-color: var(--marvel-red);
    transform: translateX(5px);
    box-shadow: 0 5px 15px rgba(237, 29, 36, 0.3);
}

.answer-btn:hover::before {
    left: 100%;
}

.answer-btn:active {
    transform: translateX(5px) scale(0.98);
}

.answer-btn.correct {
    background: linear-gradient(145deg, rgba(40, 167, 69, 0.4), rgba(40, 167, 69, 0.3));
    border-color: var(--success-green);
    animation: correctPulse 0.5s ease;
}

.answer-btn.incorrect {
    background: linear-gradient(145deg, rgba(220, 53, 69, 0.4), rgba(220, 53, 69, 0.3));
    border-color: var(--error-red);
    animation: incorrectShake 0.5s ease;
}

.answer-btn:disabled {
    cursor: not-allowed;
    opacity: 0.6;
}

/* ===========================
   Button Styles
   =========================== */
.btn-danger {
    background: linear-gradient(135deg, var(--marvel-red), #c41e3a);
    border: none;
    font-weight: 600;
    letter-spacing: 0.5px;
    transition: all var(--transition-speed) ease;
    box-shadow: 0 4px 12px rgba(237, 29, 36, 0.3);
}

.btn-danger:hover {
    background: linear-gradient(135deg, #c41e3a, var(--marvel-red));
    transform: translateY(-2px);
    box-shadow: 0 6px 16px rgba(237, 29, 36, 0.4);
}

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

.btn-outline-primary {
    border-color: rgba(255, 255, 255, 0.3);
    color: #fff;
}

.btn-outline-primary:hover {
    background: rgba(255, 255, 255, 0.1);
    border-color: #fff;
    color: #fff;
}

/* ===========================
   Difficulty Selector
   =========================== */
.difficulty-selector .btn-group {
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
    border-radius: 10px;
    overflow: hidden;
}

.difficulty-selector .btn {
    font-weight: 600;
    padding: 12px 24px;
    transition: all var(--transition-speed) ease;
}

/* ===========================
   Feedback Alert
   =========================== */
#feedback {
    border-radius: 12px;
    font-size: 1.1rem;
    font-weight: 600;
    text-align: center;
    animation: slideInDown 0.5s ease;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

/* ===========================
   Results Screen
   =========================== */
.score-display {
    padding: 30px;
    background: rgba(255, 255, 255, 0.05);
    border-radius: 15px;
    border: 2px solid rgba(237, 29, 36, 0.3);
}

/* ===========================
   Footer
   =========================== */
footer {
    background: rgba(0, 0, 0, 0.3);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

footer a:hover {
    text-decoration: underline !important;
}

/* ===========================
   Animations
   =========================== */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

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

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

@keyframes incorrectShake {
    0%, 100% {
        transform: translateX(0);
    }
    25% {
        transform: translateX(-10px);
    }
    75% {
        transform: translateX(10px);
    }
}

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

/* ===========================
   Responsive Design
   =========================== */
@media (min-width: 768px) {
    .answers-container {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .question-text {
        font-size: 1.75rem;
    }
}

@media (max-width: 576px) {
    .display-4 {
        font-size: 2rem;
    }
    
    .btn-lg {
        padding: 12px 24px;
        font-size: 1rem;
    }
    
    .difficulty-selector .btn-group {
        flex-direction: column;
        width: 100%;
    }
    
    .difficulty-selector .btn {
        border-radius: 0 !important;
    }
    
    .difficulty-selector .btn:first-child {
        border-radius: 10px 10px 0 0 !important;
    }
    
    .difficulty-selector .btn:last-child {
        border-radius: 0 0 10px 10px !important;
    }
}

/* ===========================
   Utility Classes
   =========================== */
.text-danger {
    color: var(--marvel-red) !important;
}

.bg-danger {
    background: var(--marvel-red) !important;
}

/* ===========================
   Loading Spinner
   =========================== */
.spinner-border {
    animation: spin 1s linear infinite;
}

/* ===========================
   Accessibility
   =========================== */
.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* Focus styles for accessibility */
button:focus-visible,
.btn:focus-visible {
    outline: 3px solid var(--marvel-red);
    outline-offset: 3px;
}

/* ===========================
   Print Styles
   =========================== */
@media print {
    body {
        background: white;
        color: black;
    }
    
    .quiz-card {
        box-shadow: none;
        border: 1px solid #ccc;
    }
}