/* === Base === */
body {
    margin: 0;
    font-family: "Poppins", Arial, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: radial-gradient(circle at top, #1a1a1a, #0c0c0c);
    color: #fff;
}

/* === Calculator Container === */
.calculator-container {
    backdrop-filter: blur(15px);
    background: rgba(25, 25, 25, 0.7);
    border-radius: 20px;
    padding: 25px;
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.6);
    width: 320px;
    transition: all 0.3s ease;
}

.calculator-container:hover {
    transform: scale(1.02);
}

/* === Header === */
.header {
    margin: 0 0 20px 0;
    font-size: 28px;
    font-weight: 600;
    color: #ffffff;
    text-shadow: 0 0 20px rgba(255, 255, 255, 0.7);
}

/* === Display === */
#display {
    width: 100%;
    height: 55px;
    font-size: 26px;
    margin-bottom: 20px;
    border-radius: 12px;
    border: none;
    background-color: rgba(255, 255, 255, 0.08);
    color: #fff;
    text-align: right;
    padding-right: 15px;
    outline: none;
    box-shadow: inset 0 0 10px rgba(0, 0, 0, 0.4);
}

/* === Buttons Grid === */
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 70px);
    gap: 12px;
    justify-content: center;
}

/* === Buttons === */
button {
    padding: 18px;
    font-size: 18px;
    border: none;
    border-radius: 12px;
    background: linear-gradient(145deg, #222, #1a1a1a);
    color: #fff;
    cursor: pointer;
    transition: all 0.2s ease;
    box-shadow:
        0 3px 6px rgba(0, 0, 0, 0.5),
        inset 0 -2px 5px rgba(0, 0, 0, 0.4);
}

button:hover {
    box-shadow: 0 0 5px #ffffff, 0 0 10px rgba(255, 255, 255, 0.1);
    transform: translateY(-2px);
}

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

/* === Special Buttons === */
.clear-btn {
    grid-column: span 4;
    background: #101010;
    color: #ff4b4b;
    font-weight: 600;
}

.clear-btn:hover {
    box-shadow: 0 0 10px #ff4b4b;
}