* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'poppins', sans-serif;
}

body {
    height: 100vh;
    background: linear-gradient(135deg, #7b91f3, #5e0ddf);
    display: flex;
    align-items: center;
    justify-content: center;
}

.main {
    width: 320px;
    background: #1e1e1e;
    border-radius: 15px;
    box-shadow: 0 20px 40px #000;
    overflow: hidden;
}
.display {
    width: 320px;
    height: 150px;
    padding: 15px;
    background: linear-gradient(145deg, #111, #1f1f1f);
    border-bottom: 2px solid rgba(255,255,255,0.05);
}

.display input {
    width: 100%;
    height: 100%;
    border: none;
    outline: none;
    border-radius: 12px;
    background: linear-gradient(145deg, #000, #1a1a1a);
    color: #ffffff;
    padding: 20px;
    text-align: right;
    font-size: 2rem;
    font-weight: 600;
    letter-spacing: 2px;

    /* Beautiful glow */
    box-shadow:
        inset 5px 5px 10px rgba(255,255,255,0.03),
        inset -5px -5px 10px rgba(0,0,0,0.6),
        0 0 15px rgba(123,145,243,0.4);

    transition: all 0.3s ease;
}

.display input:focus {
    box-shadow:
        inset 5px 5px 10px rgba(255,255,255,0.03),
        inset -5px -5px 10px rgba(0,0,0,0.6),
        0 0 25px rgba(94,13,223,0.7);
}

.display input::placeholder {
    color: #777;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
    padding: 20px 15px;
    justify-items: center;
}

button {
    height: 65px;
    width: 65px;
    border: none;
    border-radius: 50%;
    font-size: 1.5rem;
    font-weight: 600;
    cursor: pointer;
    color: #f1f1f1;

    background: linear-gradient(145deg, #1f1f1f, #0d0d0d);

    box-shadow:
        5px 5px 10px rgba(0,0,0,0.6),
        -3px -3px 8px rgba(255,255,255,0.05);

    transition: all 0.2s ease;
}

button:hover {
    transform: translateY(-3px);
    box-shadow:
        0 0 12px rgba(123,145,243,0.5),
        5px 5px 10px rgba(0,0,0,0.6);
}

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

.oper {
    color: #ff8c42;
}

.equal {
    background: linear-gradient(145deg, #ff8c42, #d96a00);
    color: white;
}

.zero {
    grid-column: span 2;
    width: 145px;
    height: 65px;
    border-radius: 35px;
}

.up-btn {
    background: linear-gradient(145deg, #3a3a3a, #1f1f1f);
    color: #d6d6d6;
}