:root {
    --background-color: #1a1a1a;
    --text-color: #e0e0e0;
    --primary-color: #4a4a4a;
    --secondary-color: #333333;
    --accent-color: #007bff; /* A cold blue for accents */
    --success-color: #28a745;
    --error-color: #dc3545;
    --border-color: #555555;

    --font-main: 'Helvetica Neue', Helvetica, Arial, sans-serif;
    --font-mono: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
}

body {
    background-color: var(--background-color);
    color: var(--text-color);
    font-family: var(--font-main);
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    font-size: 16px;
}

#app {
    width: 100%;
    max-width: 480px; /* Mobile-first approach */
    height: 100vh;
    border: 1px solid var(--border-color);
    box-shadow: 0 0 20px rgba(0,0,0,0.5);
    overflow-y: auto;
    display: flex;
    flex-direction: column;
}

h1, h2, h3, h4, h5, h6 {
    font-weight: 300; /* Lighter font for a cleaner look */
    color: var(--text-color);
}

button {
    background-color: var(--primary-color);
    color: var(--text-color);
    border: 1px solid var(--border-color);
    padding: 10px 15px;
    cursor: pointer;
    font-family: var(--font-main);
    border-radius: 4px;
    transition: background-color 0.2s;
}

button:hover {
    background-color: #5a5a5a;
}