.ti84-calculator {
    width: 400px;
    margin: 30px auto;
    padding: 15px;
    border-radius: 15px;
    background: #000;
    color: #0ff;
    box-shadow: 0 0 20px #0ff;
    font-family: 'Courier New', monospace;
}
.ti84-display {
    width: 100%;
    height: 60px;
    background: #111;
    color: #0ff;
    border: none;
    font-size: 22px;
    padding: 10px;
    border-radius: 10px;
    margin-bottom: 10px;
}
.ti84-buttons {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 10px;
}
.ti84-buttons button {
    padding: 15px;
    font-size: 18px;
    border: none;
    border-radius: 12px;
    background-color: #111;
    color: #0ff;
    cursor: pointer;
}
.ti84-buttons button:hover {
    background-color: #0ff;
    color: #000;
}