body {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    margin-top: 50px;
    background: #121212;
    font-family: 'Roboto', sans-serif;
    color: #fff;
}

h1 {
    font-size: 2.2rem;
    margin-bottom: 15px;
    color: #ffffff;
    text-transform: uppercase;
    letter-spacing: 2px;
    font-weight: 300;
}

#container {
    text-align: center;
    padding: 25px;
    background: #1e1e1e;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.5);
    width: 90%;
    max-width: 400px;
}

#display {
    font-family: 'Roboto Mono', monospace;
    font-size: 2.5rem;
    margin-bottom: 20px;
    padding: 15px 0;
    border: none;
    background: transparent;
    color: #00ffc3;
    border-bottom: 2px solid rgba(255, 255, 255, 0.2);
    text-align: center;
    letter-spacing: 2px;
}

.control button {
    font-size: 1rem;
    margin: 5px;
    padding: 10px 20px;
    border: 1px solid #333; 
    border-radius: 6px;
    background: #262626;
    color: #fff;
    cursor: pointer;
    transition: all 0.2s ease-in-out;
}

.control button:hover {
    background: #00ffc3;
    color: #121212;
    transform: scale(1.05);
}

.control button:active {
    transform: scale(0.98);
    background: #00b394; 
}