:root {
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --accent: #10b981;
    --bg-gradient: linear-gradient(135deg, #f8fafc 0%, #f1f5f9 100%);
}

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    background: var(--bg-gradient);
    min-height: 100vh;
    color: #1e293b;
}

.glass-card {
    background: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(12px);
    border: 1px solid rgba(255, 255, 255, 0.3);
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.05);
}

.slide-up {
    animation: slideUp 0.5s ease-out;
}

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

/* Flashcard Core Logic */
.card-inner {
    transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
    transform-style: preserve-3d;
    cursor: pointer;
}
.card-flipped .card-inner {
    transform: rotateY(180deg);
}
.card-front, .card-back {
    backface-visibility: hidden;
    position: absolute;
    top: 0; left: 0; width: 100%; height: 100%;
}
.card-back {
    transform: rotateY(180deg);
}

/* Navigation Animations */
@keyframes navNext {
    0% { transform: scale(1) rotateY(0); opacity: 1; }
    50% { transform: scale(0.9) rotateY(-90deg); opacity: 0.3; }
    51% { transform: scale(0.9) rotateY(90deg); opacity: 0.3; }
    100% { transform: scale(1) rotateY(0); opacity: 1; }
}
@keyframes navPrev {
    0% { transform: scale(1) rotateY(0); opacity: 1; }
    50% { transform: scale(0.9) rotateY(90deg); opacity: 0.3; }
    51% { transform: scale(0.9) rotateY(-90deg); opacity: 0.3; }
    100% { transform: scale(1) rotateY(0); opacity: 1; }
}
.animate-nav-next { animation: navNext 0.5s ease-in-out; }
.animate-nav-prev { animation: navPrev 0.5s ease-in-out; }

.hide { display: none !important; }

.lesson-content h1 { font-size: 1.8rem; font-weight: 800; margin-bottom: 1rem; color: var(--primary); }
.lesson-content h2 { font-size: 1.4rem; font-weight: 700; margin-top: 1.5rem; margin-bottom: 0.5rem; }
.lesson-content p { margin-bottom: 1rem; line-height: 1.7; }
.lesson-content ul { list-style-type: disc; margin-left: 1.5rem; margin-bottom: 1rem; }
.lesson-content strong { color: var(--primary-dark); }
.lesson-content .key-takeaways { 
    margin-top: 2rem; 
    padding: 1.5rem; 
    background: #f8fafc; 
    border-radius: 1.5rem; 
    border: 1px solid #e2e8f0;
}

.option-correct { border-color: #10b981 !important; background-color: #ecfdf5 !important; color: #065f46 !important; }
.option-wrong { border-color: #ef4444 !important; background-color: #fef2f2 !important; color: #991b1b !important; }
.option-disabled { pointer-events: none; opacity: 0.7; }

#ai-loader {
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(8px);
}