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

body {
    font-family: system-ui, sans-serif;
    background: #f4f6fa;
    color: #1f2937;
    min-height: 100vh;
}

.site-header {
    background: #2563eb;
    color: #fff;
    padding: 1rem 2rem;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

.container {
    max-width: 720px;
    margin: 2rem auto;
    padding: 0 1rem;
}

.chat-box {
    background: #fff;
    border-radius: 0.75rem;
    padding: 1.5rem;
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.08);
}

.chat-box h2 {
    margin-bottom: 1rem;
    color: #111827;
}

.message-list {
    list-style: none;
    margin-bottom: 1.5rem;
    max-height: 400px;
    overflow-y: auto;
}

.message {
    background: #f9fafb;
    border: 1px solid #e5e7eb;
    border-radius: 0.5rem;
    padding: 0.75rem 1rem;
    margin-bottom: 0.5rem;
}

.message.empty {
    text-align: center;
    color: #6b7280;
    font-style: italic;
}

.message-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: 0.25rem;
    font-size: 0.9rem;
}

.timestamp {
    color: #6b7280;
}

.message-body {
    white-space: pre-wrap;
}

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

.form-input {
    width: 100%;
    padding: 0.5rem 0.75rem;
    border: 1px solid #d1d5db;
    border-radius: 0.5rem;
    font: inherit;
    resize: vertical;
}

.form-input:focus {
    outline: none;
    border-color: #2563eb;
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.2);
}

.message-form button {
    align-self: flex-end;
    background: #2563eb;
    color: #fff;
    border: none;
    border-radius: 0.5rem;
    padding: 0.5rem 1.25rem;
    cursor: pointer;
    font: inherit;
}

.message-form button:hover {
    background: #1d4ed8;
}