/* ============================================================
   TFA Lernapp - Base Styles (Reset, Typography, Utilities)
   ============================================================ */

/* Reset */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: var(--font-family);
    font-size: var(--text-base);
    line-height: var(--leading-normal);
    color: var(--text-primary);
    background: var(--bg-primary);
    min-height: 100vh;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Background Gradient */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        radial-gradient(ellipse at 20% 20%, rgba(99, 102, 241, 0.08) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 80%, rgba(245, 158, 11, 0.05) 0%, transparent 50%),
        radial-gradient(ellipse at 50% 50%, rgba(16, 185, 129, 0.03) 0%, transparent 70%);
    pointer-events: none;
    z-index: -1;
}

a {
    color: var(--primary-400);
    text-decoration: none;
    transition: color var(--transition-fast);
}
a:hover {
    color: var(--primary-300);
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: var(--leading-tight);
    color: var(--text-primary);
}

h1 { font-size: var(--text-4xl); }
h2 { font-size: var(--text-3xl); }
h3 { font-size: var(--text-2xl); }
h4 { font-size: var(--text-xl); }
h5 { font-size: var(--text-lg); }
h6 { font-size: var(--text-base); }

p {
    color: var(--text-secondary);
    line-height: var(--leading-relaxed);
}

/* Selection */
::selection {
    background: var(--primary-500);
    color: white;
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}
::-webkit-scrollbar-track {
    background: transparent;
}
::-webkit-scrollbar-thumb {
    background: var(--neutral-600);
    border-radius: var(--radius-full);
}
::-webkit-scrollbar-thumb:hover {
    background: var(--neutral-500);
}

/* Focus Visible */
:focus-visible {
    outline: 2px solid var(--primary-500);
    outline-offset: 2px;
}

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

.text-center { text-align: center; }
.text-right { text-align: right; }
.text-sm { font-size: var(--text-sm); }
.text-xs { font-size: var(--text-xs); }
.text-lg { font-size: var(--text-lg); }
.text-secondary { color: var(--text-secondary); }
.text-success { color: var(--success-500); }
.text-error { color: var(--error-500); }
.text-warning { color: var(--warning-500); }
.text-primary-color { color: var(--primary-400); }

.font-medium { font-weight: 500; }
.font-semibold { font-weight: 600; }
.font-bold { font-weight: 700; }

.mt-sm { margin-top: var(--space-sm); }
.mt-md { margin-top: var(--space-md); }
.mt-lg { margin-top: var(--space-lg); }
.mt-xl { margin-top: var(--space-xl); }
.mb-sm { margin-bottom: var(--space-sm); }
.mb-md { margin-bottom: var(--space-md); }
.mb-lg { margin-bottom: var(--space-lg); }

.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.gap-sm { gap: var(--space-sm); }
.gap-md { gap: var(--space-md); }
.gap-lg { gap: var(--space-lg); }
.flex-1 { flex: 1; }
.flex-wrap { flex-wrap: wrap; }

.hidden { display: none !important; }
.block { display: block; }

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

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

@keyframes slideInRight {
    from { opacity: 0; transform: translateX(30px); }
    to { opacity: 1; transform: translateX(0); }
}

@keyframes slideInLeft {
    from { opacity: 0; transform: translateX(-30px); }
    to { opacity: 1; transform: translateX(0); }
}

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

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.6; }
}

@keyframes shimmer {
    0% { background-position: -200% 0; }
    100% { background-position: 200% 0; }
}

@keyframes progressFill {
    from { width: 0; }
}

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

.animate-fade-in {
    animation: fadeIn var(--transition-base) ease-out;
}

.animate-fade-in-up {
    animation: fadeInUp var(--transition-slow) ease-out;
}

.animate-scale-in {
    animation: scaleIn var(--transition-base) ease-out;
}

/* Spinner */
.spinner {
    width: 24px;
    height: 24px;
    border: 3px solid rgba(255, 255, 255, 0.2);
    border-top-color: var(--primary-400);
    border-radius: 50%;
    animation: spin 0.6s linear infinite;
    display: inline-block;
}

/* Select Elements (Dark Mode) */
select {
    -webkit-appearance: none;
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%2394a3b8' viewBox='0 0 16 16'%3E%3Cpath d='M8 11L3 6h10z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 0.75rem center;
    padding-right: 2rem;
}

select option {
    background: var(--bg-secondary);
    color: var(--text-primary);
}

/* Touch-Friendly Improvements */
@media (pointer: coarse) {
    .btn {
        min-height: 44px;
    }
    .nav-item {
        min-height: 44px;
    }
    .option-item {
        min-height: 48px;
    }
    .topic-checkbox {
        min-height: 48px;
    }
}

/* Safe Area (Notch devices) */
@supports (padding: env(safe-area-inset-bottom)) {
    .quiz-nav {
        padding-bottom: env(safe-area-inset-bottom);
    }
    .sidebar-footer {
        padding-bottom: calc(var(--space-md) + env(safe-area-inset-bottom));
    }
    .mobile-header {
        padding-top: env(safe-area-inset-top);
    }
}