* {
    box-sizing: border-box;
}

body{
    font-family: Arial, Helvetica, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    background: radial-gradient(circle at top, #111, #000);
}

.calculadora{
    background-color: #0b0b0b;
    padding: 30px;
    border-radius: 16px;
    width: min(90vw, 600px); /* 🔥 RESPONSIVO */
    box-shadow: 0 0 25px rgba(0,0,0,0.8);
    animation: bordaRGB 6s linear infinite;
}

@keyframes bordaRGB {
    0%   { box-shadow: 0 0 20px #ff004c; }
    25%  { box-shadow: 0 0 20px #00e5ff; }
    50%  { box-shadow: 0 0 20px #39ff14; }
    75%  { box-shadow: 0 0 20px #8b5cf6; }
    100% { box-shadow: 0 0 20px #ff004c; }
}

#visor {
    width: 100%;
    height: 90px;
    font-size: clamp(28px, 5vw, 40px);
    text-align: right;
    margin-bottom: 20px;
    padding: 15px;
    background-color: #000;
    color: #00e5ff;
    border: none;
    border-radius: 8px;
    box-shadow: inset 0 0 15px #00e5ff;
}

.botoes {
    display: grid;
    grid-template-columns: repeat(4,1fr);
    gap: 12px;
}

button {
    padding: 22px;
    font-size: clamp(18px, 4vw, 26px);
    border: none;
    border-radius: 12px;
    background-color: #1f1f1f;
    color: white;
    cursor: pointer;
    transition: 
        transform 0.1s,
        box-shadow 0.2s,
        background-color 0.3s;
}

button:hover {
    box-shadow: 0 0 15px #39ff14;
    background-color: #2a2a2a;
}

button:active {
    transform: scale(0.95);
}

.operador {
    background-color: #ff2e2e
}

.operador:hover {
    box-shadow: 0 0 18px #ff2e2e;
}

.operador:last-child {
    background: linear-gradient(45deg, #ff004c, #8b5cf6, #00e5ff);
    background-size: 300% 300%;
    animation: botaoRGB 3s infinite;
    font-size: 32px;
}

@keyframes botaoRGB {
    0% { background-position: 0% 50%; box-shadow: 0 0 20px #ff004c; }
    50% { background-position: 100% 50%; box-shadow: 0 0 25px #00e5ff; }
    100% { background-position: 0% 50%; box-shadow: 0 0 20px #ff004c; }
}