/* Base Styles */
:root {
    --primary-color: #0078d4;
    --primary-hover: #106ebe;
    --success-color: #107c10;
    --success-bg: #dff6dd;
    --error-color: #d13438;
    --error-bg: #fde7e9;
    --warning-color: #ffb900;
    --warning-bg: #fff4ce;
    --text-color: #323130;
    --text-muted: #605e5c;
    --bg-color: #faf9f8;
    --card-bg: #ffffff;
    --border-color: #edebe9;
    --hover-bg: #f3f2f1;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Segoe UI', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.5;
    min-height: 100vh;
}

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

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.625rem 1.25rem;
    border: none;
    border-radius: 4px;
    font-size: 0.9375rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.15s ease;
    text-decoration: none;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
}

.btn-primary:hover:not(:disabled) {
    background-color: var(--primary-hover);
}

.btn-secondary {
    background-color: transparent;
    color: var(--primary-color);
    border: 1px solid var(--primary-color);
}

.btn-secondary:hover:not(:disabled) {
    background-color: var(--hover-bg);
}

/* Breadcrumb Navigation */
.breadcrumb-nav {
    background: var(--card-bg);
    border-bottom: 1px solid var(--border-color);
    padding: 0.75rem 1rem;
}

.breadcrumb-nav a {
    color: var(--primary-color);
    text-decoration: none;
    font-size: 0.9375rem;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

.breadcrumb-nav a:hover {
    text-decoration: underline;
}

.breadcrumb-nav .breadcrumb-arrow {
    font-size: 0.75rem;
    color: var(--text-muted);
}

/* Main Header */
.main-header {
    background: linear-gradient(135deg, var(--primary-color) 0%, #005a9e 100%);
    color: white;
    padding: 3rem 2rem;
    text-align: center;
}

.main-header h1 {
    font-size: 2.5rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.main-header p {
    font-size: 1.125rem;
    opacity: 0.9;
}

/* Exam Selector */
.exam-selector {
    max-width: 1100px;
    margin: 0 auto;
    padding: 2rem 1rem;
}

.exam-selector h2 {
    text-align: center;
    margin-bottom: 2rem;
    font-size: 1.5rem;
    color: var(--text-color);
}

.exam-cards {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 1.5rem;
}

@media (min-width: 1000px) {
    .exam-cards {
        grid-template-columns: repeat(3, 1fr);
    }
}

.exam-card {
    background: var(--card-bg);
    border-radius: 8px;
    padding: 1.5rem;
    text-decoration: none;
    color: inherit;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
    transition: all 0.2s ease;
    border: 2px solid transparent;
}

.exam-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.12);
    border-color: var(--primary-color);
}

.exam-code {
    display: inline-block;
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 4px;
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
}

.exam-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-color);
}

.exam-description {
    color: var(--text-muted);
    font-size: 0.9375rem;
    margin-bottom: 1rem;
}

.exam-meta {
    display: flex;
    gap: 1rem;
    font-size: 0.875rem;
    color: var(--text-muted);
}

/* Footer */
.main-footer {
    text-align: center;
    padding: 2rem;
    color: var(--text-muted);
    font-size: 0.875rem;
}

/* Loading Spinner */
.loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 4rem;
}

.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--border-color);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

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

.loading p {
    margin-top: 1rem;
    color: var(--text-muted);
}

/* Error Message */
.error-message {
    text-align: center;
    padding: 3rem;
    background: var(--card-bg);
    border-radius: 8px;
    max-width: 500px;
    margin: 2rem auto;
}

.error-message h2 {
    color: var(--error-color);
    margin-bottom: 1rem;
}

.error-message p {
    margin-bottom: 1.5rem;
    color: var(--text-muted);
}

/* Responsive */
@media (max-width: 600px) {
    .main-header {
        padding: 2rem 1rem;
    }

    .main-header h1 {
        font-size: 1.75rem;
    }

    .exam-cards {
        grid-template-columns: 1fr;
    }
}