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

/* ===== Utility Classes ===== */
.hidden {
    display: none !important;
}

.screen {
    display: none !important;
    min-height: 100vh;
}

.screen.active {
    display: block !important;
}

.content-section {
    display: none;
}

.content-section.active {
    display: block;
}

/* ===== Loading Spinner ===== */
.loading-spinner {
    display: inline-block;
    width: 48px;
    height: 48px;
    border: 4px solid var(--gray-200);
    border-top: 4px solid var(--primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: 1rem;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* ===== Loading States ===== */
.skeleton {
    background: linear-gradient(90deg, var(--gray-200) 0%, var(--gray-100) 50%, var(--gray-200) 100%);
    background-size: 200% 100%;
    animation: shimmer 1.5s infinite;
}

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

/* ===== Animations ===== */
.fade-in {
    animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.slide-up {
    animation: slideUp 0.3s ease;
}

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

/* ===== Reduced Motion ===== */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

/* ===== Skip Navigation ===== */
.skip-link {
    position: absolute;
    top: -100%;
    left: 1rem;
    z-index: 10000;
    padding: 0.75rem 1.25rem;
    background: var(--primary);
    color: var(--on-primary);
    border-radius: 0 0 0.5rem 0.5rem;
    font-weight: 600;
    text-decoration: none;
}

.skip-link:focus {
    top: 0;
}

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

/* ===== Selection ===== */
::selection {
    background: var(--primary);
    color: var(--on-primary);
}

::-moz-selection {
    background: var(--primary);
    color: var(--on-primary);
}

/* ===== SW Update Banner ===== */
.sw-update-banner {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 10001;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    padding: 0.6rem 1rem;
    background: var(--primary);
    color: var(--on-primary);
    font-size: var(--text-sm);
    font-weight: 500;
    box-shadow: var(--shadow-md);
    animation: slideDown 0.3s ease;
}

.sw-update-banner[hidden] {
    display: none;
}

.sw-update-banner button {
    background: var(--on-primary);
    color: var(--primary);
    border: none;
    border-radius: var(--radius-sm);
    padding: 0.3rem 0.75rem;
    font-size: var(--text-sm);
    font-weight: 600;
    cursor: pointer;
    white-space: nowrap;
}

@keyframes slideDown {
    from { transform: translateY(-100%); opacity: 0; }
    to { transform: translateY(0); opacity: 1; }
}