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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background: #f5f5f5;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    padding: 2rem;
}

main {
    max-width: 500px;
    width: 100%;
}

h1 {
    font-size: 2rem;
    margin-bottom: 0.5rem;
    color: #333;
}

.subtitle {
    color: #666;
    margin-bottom: 2rem;
}

.subtitle a {
    color: #0066cc;
    text-decoration: none;
}

.subtitle a:hover {
    text-decoration: underline;
}

.input-section {
    margin-bottom: 1.5rem;
}

#isbn-input {
    width: 100%;
    padding: 1rem;
    font-size: 1.1rem;
    border: 2px solid #ddd;
    border-radius: 8px;
    outline: none;
    transition: border-color 0.2s;
}

#isbn-input:focus {
    border-color: #0066cc;
}

.samples {
    margin-top: 0.75rem;
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    align-items: center;
}

.samples span {
    color: #666;
    font-size: 0.9rem;
}

.sample {
    background: white;
    border: 1px solid #ddd;
    border-radius: 4px;
    padding: 0.25rem 0.5rem;
    font-family: "SF Mono", Monaco, monospace;
    font-size: 0.85rem;
    cursor: pointer;
    transition: all 0.2s;
}

.sample:hover {
    border-color: #0066cc;
    background: #f0f7ff;
}

.results {
    background: white;
    border-radius: 8px;
    padding: 1rem;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

.result-row {
    display: flex;
    justify-content: space-between;
    padding: 0.75rem 0;
    border-bottom: 1px solid #eee;
}

.result-row:last-child {
    border-bottom: none;
}

.label {
    color: #666;
    font-weight: 500;
}

.value {
    color: #333;
    font-family: "SF Mono", Monaco, monospace;
}

.value.valid {
    color: #22863a;
}

.value.invalid {
    color: #cb2431;
}

.error {
    background: #ffeef0;
    color: #cb2431;
    padding: 1rem;
    border-radius: 8px;
    margin-top: 1rem;
}

.hidden {
    display: none;
}