body {
    background: radial-gradient(circle at top, #0a0a0f, #000);
    font-family: 'Orbitron', sans-serif;

    display: flex;
    flex-direction: column; /* 🔥 IMPORTANTE */
    justify-content: center;
    align-items: center;

    height: 100vh;
    margin: 0;
}

/* Contenedor */
.calculator {
    background: #111;
    border-radius: 15px;
    padding: 20px;
    box-shadow: 0 0 30px #00f7ff55;
    width: 320px;
}

/* Pantalla */
.display {
    background: black;
    color: #00f7ff;
    font-size: 2em;
    padding: 15px;
    border-radius: 10px;
    margin-bottom: 15px;
    text-align: right;
    box-shadow: inset 0 0 10px #00f7ff;
    overflow-x: auto;
}

/* Botones */
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

button {
    background: #111;
    border: 1px solid #00f7ff;
    color: #00f7ff;
    font-size: 1.2em;
    padding: 15px;
    border-radius: 10px;
    cursor: pointer;
    transition: 0.2s;
}

button:hover {
    background: #00f7ff;
    color: black;
    box-shadow: 0 0 15px #00f7ff;
}

button:active {
    transform: scale(0.95);
}
/* Encabezado */
.title {
    color: #00f7ff;
    text-align: center;
    margin-bottom: 20px;
    text-shadow: 0 0 10px #00f7ff;
}

/* Modal futurista */
.modal {
    position: fixed;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.9);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.modal-content {
    background: #111;
    border: 1px solid #00f7ff;
    padding: 30px;
    border-radius: 15px;
    text-align: center;
    box-shadow: 0 0 25px #00f7ff55;
}

.modal-content h2 {
    color: #00f7ff;
    margin-bottom: 15px;
}

.modal-content input {
    padding: 10px;
    width: 80%;
    margin-bottom: 15px;
    border-radius: 8px;
    border: 1px solid #00f7ff;
    background: black;
    color: #00f7ff;
    text-align: center;
}

.modal-content button {
    width: 100%;
}