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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    line-height: 1.6;
    color: #333;
    background: #f5f5f5;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    padding: 2rem;
}

.container {
    max-width: 600px;
    width: 100%;
    background: white;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

header {
    text-align: center;
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid #eee;
}

h1 {
    font-size: 1.5rem;
    color: #222;
    margin-bottom: 0.25rem;
}

.subtitle {
    color: #666;
    font-size: 0.875rem;
}

main {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

label {
    font-weight: 500;
    font-size: 0.875rem;
    color: #444;
}

input[type="file"] {
    padding: 0.5rem;
    border: 1px solid #ddd;
    border-radius: 4px;
    font-size: 0.875rem;
}

button {
    padding: 0.75rem 1.5rem;
    background: #2563eb;
    color: white;
    border: none;
    border-radius: 4px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: background 0.2s;
}

button:hover {
    background: #1d4ed8;
}

.result {
    padding: 1rem;
    border-radius: 4px;
    margin-top: 1rem;
}

.result h2 {
    font-size: 1rem;
    margin-bottom: 0.75rem;
}

.result pre {
    background: #f8f9fa;
    padding: 1rem;
    border-radius: 4px;
    overflow-x: auto;
    font-size: 0.875rem;
    font-family: 'Monaco', 'Menlo', 'Ubuntu Mono', monospace;
}

.result.hidden {
    display: none;
}

.result.valid {
    background: #dcfce7;
    border: 1px solid #86efac;
}

.result.invalid {
    background: #fee2e2;
    border: 1px solid #fca5a5;
}

footer {
    margin-top: 2rem;
    padding-top: 1rem;
    border-top: 1px solid #eee;
    text-align: center;
}

footer p {
    font-size: 0.75rem;
    color: #888;
}