:root {
    --primary: #4f46e5;
    --primary-hover: #4338ca;
    --bg: #f3f4f6;
    --card-bg: #ffffff;
    --text: #1f2937;
    --text-muted: #6b7280;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg);
    color: var(--text);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    padding: 20px;
}

.card {
    background: var(--card-bg);
    padding: 2.5rem;
    border-radius: 16px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.05);
    width: 100%;
    max-width: 450px;
}

h1 {
    margin: 0 0 0.25rem 0;
    font-size: 1.8rem;
}

.subtitle {
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-top: 0;
    margin-bottom: 2rem;
}

.guestbook-form {
    display: flex;
    gap: 8px;
    margin-bottom: 2rem;
}

input[type="text"] {
    flex: 1;
    padding: 12px 16px;
    border: 1px solid #d1d5db;
    border-radius: 8px;
    font-size: 1rem;
    outline: none;
    transition: border-color 0.2s;
}

input[type="text"]:focus {
    border-color: var(--primary);
}

button {
    background-color: var(--primary);
    color: white;
    border: none;
    padding: 12px 20px;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.2s;
}

button:hover {
    background-color: var(--primary-hover);
}

h2 {
    font-size: 1.2rem;
    border-bottom: 2px solid var(--bg);
    padding-bottom: 8px;
}

.message-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.message-list li {
    background: #f9fafb;
    padding: 12px 16px;
    border-radius: 8px;
    margin-bottom: 8px;
    border: 1px solid #edf2f7;
    word-break: break-word;
}

.message-list li.empty {
    color: var(--text-muted);
    font-style: italic;
    background: transparent;
    border: none;
}