/* CSS Custom Properties */
:root {
    --primary-purple: #6B46C1;
    --primary-blue: #3B82F6;
    --success-green: #10B981;
    --danger-red: #EF4444;
    --warning-yellow: #F59E0B;
    --neutral-orange: #F97316;
    --text-white: #FFFFFF;
    --text-dark: #1F2937;
    --glass-bg: rgba(255, 255, 255, 0.1);
    --glass-border: rgba(255, 255, 255, 0.2);
    --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);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: linear-gradient(135deg, var(--primary-purple) 0%, var(--primary-blue) 100%);
    color: var(--text-white);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    line-height: 1.6;
}

/* Navigation */
.game-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem;
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--glass-border);
}

.home-link {
    color: var(--text-white);
    text-decoration: none;
    font-weight: 600;
    transition: opacity 0.3s ease;
}

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

.game-logo {
    font-size: 1.5rem;
    font-weight: bold;
    text-shadow: 1px 1px 2px rgba(0, 0, 0, 0.3);
}

/* Layout Components */
.game-container {
    max-width: 800px;
    margin: 0 auto;
    padding: 1rem;
    flex: 1;
    display: flex;
    flex-direction: column;
}

.game-header {
    text-align: center;
    margin-bottom: 1.5rem;
}

.game-subtitle {
    font-size: 1.1rem;
    opacity: 0.9;
    margin-bottom: 1rem;
}

/* Mobile Header Grid */
.mobile-header-grid {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    gap: 0.5rem;
    align-items: center;
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: 1rem;
    padding: 0.75rem;
    margin-bottom: 1rem;
}

.header-stat {
    text-align: center;
    font-size: 0.9rem;
}

.header-stat.left {
    text-align: left;
}

.header-stat.right {
    text-align: right;
}

.stat-label {
    display: block;
    font-size: 0.75rem;
    opacity: 0.8;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.stat-value {
    display: block;
    font-size: 1.1rem;
    font-weight: bold;
    margin-top: 0.2rem;
}

/* Game Content Area */
.game-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

/* Flashcard */
.flashcard-container {
    perspective: 1000px;
    height: 300px;
    margin: 0 auto;
    width: 100%;
    max-width: 400px;
}

.flashcard {
    position: relative;
    width: 100%;
    height: 100%;
    transform-style: preserve-3d;
    transition: transform 0.6s ease;
    cursor: pointer;
}

.flashcard.flipped {
    transform: rotateY(180deg);
}

.flashcard-face {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    border-radius: 1.5rem;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    padding: 2rem;
    text-align: center;
    box-shadow: var(--shadow-xl);
    border: 2px solid var(--glass-border);
}

.flashcard-front {
    background: linear-gradient(135deg, var(--glass-bg), rgba(255, 255, 255, 0.05));
    backdrop-filter: blur(15px);
}

.flashcard-back {
    background: linear-gradient(135deg, var(--success-green), #059669);
    transform: rotateY(180deg);
}

.card-text {
    font-size: 2rem;
    font-weight: bold;
    margin-bottom: 1rem;
    word-wrap: break-word;
}

.card-pronunciation {
    font-size: 1.2rem;
    opacity: 0.8;
    font-style: italic;
    margin-bottom: 0.5rem;
}

.card-type {
    font-size: 0.9rem;
    opacity: 0.7;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.flip-hint {
    position: absolute;
    bottom: 1rem;
    font-size: 0.8rem;
    opacity: 0.6;
}

/* Control Buttons */
.controls-container {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 0.75rem;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: var(--shadow-lg);
    min-height: 44px;
    min-width: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    text-decoration: none;
}

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

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

.btn-know {
    background: linear-gradient(135deg, var(--success-green), #059669);
    color: var(--text-white);
}

.btn-learn {
    background: linear-gradient(135deg, var(--warning-yellow), #D97706);
    color: var(--text-white);
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-purple), var(--primary-blue));
    color: var(--text-white);
}

.btn-secondary {
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    color: var(--text-white);
}

/* Progress Section */
.progress-section {
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: 1rem;
    padding: 1.5rem;
    margin-top: 1rem;
}

.progress-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: 1rem;
    text-align: center;
}

.progress-item {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.progress-number {
    font-size: 2rem;
    font-weight: bold;
    color: var(--success-green);
}

.progress-label {
    font-size: 0.9rem;
    opacity: 0.8;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* Feedback Area */
.feedback-container {
    min-height: 4rem;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: 1rem;
    padding: 1rem;
    text-align: center;
}

.feedback-message {
    font-size: 1.1rem;
    font-weight: 600;
}

.feedback-success {
    color: var(--success-green);
}

.feedback-learning {
    color: var(--warning-yellow);
}

/* Setup Screen */
.setup-screen {
    text-align: center;
    max-width: 500px;
    margin: 0 auto;
}

.setup-options {
    display: grid;
    gap: 1rem;
    margin: 2rem 0;
}

.option-card {
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: 1rem;
    padding: 1.5rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

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

.option-card.selected {
    border-color: var(--success-green);
    background: rgba(16, 185, 129, 0.1);
}

.option-title {
    font-size: 1.2rem;
    font-weight: bold;
    margin-bottom: 0.5rem;
}

.option-description {
    opacity: 0.8;
    font-size: 0.9rem;
}

/* Instructions Card */
.instructions-card {
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: 1rem;
    padding: 1.5rem;
    margin-top: 2rem;
    text-align: left;
}

.instructions-card h3 {
    margin-bottom: 1rem;
    text-align: center;
}

.instructions-card ul {
    list-style: none;
    margin-bottom: 1rem;
}

.instructions-card li {
    margin-bottom: 0.5rem;
    padding-left: 1rem;
    position: relative;
}

.instructions-card li::before {
    content: '•';
    position: absolute;
    left: 0;
    color: var(--success-green);
    font-weight: bold;
}

.keyboard-shortcuts {
    font-size: 0.9rem;
    opacity: 0.8;
    text-align: center;
    padding-top: 1rem;
    border-top: 1px solid var(--glass-border);
}

/* Results Screen */
.results-screen {
    text-align: center;
    max-width: 500px;
    margin: 0 auto;
}

.results-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 1rem;
    margin: 2rem 0;
}

.results-card {
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: 1rem;
    padding: 1.5rem;
}

.results-number {
    font-size: 2.5rem;
    font-weight: bold;
    color: var(--success-green);
    margin-bottom: 0.5rem;
}

.results-label {
    opacity: 0.8;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* Responsive Design */
@media (max-width: 640px) {
    .game-container {
        padding: 0.75rem;
    }

    .game-nav {
        padding: 0.75rem;
    }

    .game-logo {
        font-size: 1.25rem;
    }

    .flashcard-container {
        height: 250px;
    }

    .card-text {
        font-size: 1.5rem;
    }

    .card-pronunciation {
        font-size: 1rem;
    }

    .controls-container {
        gap: 0.75rem;
    }

    .btn {
        padding: 0.6rem 1.2rem;
        font-size: 0.9rem;
    }

    .mobile-header-grid {
        padding: 0.5rem;
        gap: 0.25rem;
    }

    .header-stat {
        font-size: 0.8rem;
    }

    .stat-value {
        font-size: 1rem;
    }
}

@media (max-width: 480px) {
    .flashcard-container {
        height: 220px;
    }

    .card-text {
        font-size: 1.3rem;
    }

    .flashcard-face {
        padding: 1.5rem;
    }

    .setup-options {
        gap: 0.75rem;
    }

    .option-card {
        padding: 1.25rem;
    }

    .results-stats {
        grid-template-columns: 1fr;
        gap: 0.75rem;
    }

    .results-card {
        padding: 1.25rem;
    }
}

/* Animations */
@keyframes celebrate {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.05); }
}

.celebrate {
    animation: celebrate 0.6s ease-in-out;
}

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

.fade-in {
    animation: fadeIn 0.5s ease-out;
}

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