/**
 * css/core/layout.css
 * App shell: Header, Navigation, Sections, Footer
 */

/* =============================================================================
   HEADER
   ============================================================================= */
.header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-light);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0.875rem 1.5rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
}

/* Logo */
.logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    transition: var(--transition-base);
}

.logo:hover {
    transform: scale(1.02);
}

a.logo {
    text-decoration: none;
    color: inherit;
}

.logo-text {
    font-size: 1.375rem;
    font-weight: 800;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: -0.02em;
}

/* Navigation */
.nav {
    display: flex;
    gap: 0.375rem;
    background: var(--bg-tertiary);
    padding: 0.25rem;
    border-radius: var(--radius-full);
}

.nav-btn {
    padding: 0.5rem 1.125rem;
    border: none;
    background: none;
    color: var(--text-secondary);
    font-size: 0.875rem;
    font-weight: 500;
    border-radius: var(--radius-full);
    cursor: pointer;
    transition: var(--transition-base);
    white-space: nowrap;
}

.nav-btn:hover:not(.disabled):not(.active) {
    color: var(--text-primary);
    background: rgba(255, 255, 255, 0.8);
}

.nav-btn.active {
    color: white;
    background: var(--gradient-primary);
    box-shadow: var(--shadow-primary-sm);
    cursor: default;
    pointer-events: none;
}

.nav-btn.disabled,
.nav-btn:disabled {
    opacity: 0.4;
    cursor: not-allowed;
    pointer-events: none;
}

/* Language Select */
.lang-select {
    padding: 0.5rem 0.875rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 0.875rem;
    transition: var(--transition-base);
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%23475569' d='M6 8L1 3h10z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 0.625rem center;
    background-size: 10px;
    padding-right: 2rem;
}

.lang-select:hover {
    border-color: var(--primary);
}

.lang-select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: var(--shadow-primary-focus);
}

/* =============================================================================
   SECTIONS
   ============================================================================= */
.section {
    display: none;
    flex: 1;
    padding: 2rem 1.5rem;
    padding-bottom: 100px;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
    animation: fadeIn 0.4s ease-out;
}

.section.active {
    display: block;
}

.section-title {
    font-size: 2rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 2.5rem;
    letter-spacing: -0.02em;
}

/* =============================================================================
   FOOTER
   ============================================================================= */
.footer {
    border-top: 1px solid var(--border-light);
    padding: 1rem 1.5rem;
    background: var(--bg-secondary);
    margin-top: auto;
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 1.5rem;
}

.footer-brand {
    font-size: 0.9rem;
    color: var(--text-muted);
}

.footer-links {
    display: flex;
    gap: 0.75rem;
}

.footer-links a {
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    background: var(--bg-tertiary);
    color: var(--text-secondary);
    transition: var(--transition-base);
    border: 1px solid var(--border-light);
}

.footer-links a:hover {
    background: var(--gradient-primary);
    color: white;
    border-color: transparent;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

.footer-links svg {
    width: 18px;
    height: 18px;
    fill: currentColor;
}