/* Reset & Fonts */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Poppins', sans-serif;
}

body {
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: #000000;
}

/* Calculator Container */
.calculator-container {
    padding: 20px;
}

/* Calculator Card */
.calculator {
    width: 350px;
    background: rgba(30, 30, 30, 0.85);
    backdrop-filter: blur(15px);
    padding: 25px;
    border-radius: 25px;
    box-shadow: 0 10px 40px rgba(255, 255, 0, 0.25);
}

/* Display */
.display {
    background: rgba(0, 0, 0, 0.2);
    border-radius: 20px;
    padding: 15px;
    margin-bottom: 20px;
    text-align: right;
    color: #fff;
    box-shadow: inset 0 0 10px rgba(255, 255, 0, 0.2);
}

.history {
    font-size: 14px;
    color: #ffd700;
    min-height: 18px;
    letter-spacing: 0.5px;
}

.output {
    font-size: 36px;
    font-weight: 700;
    color: #fff200;
    word-wrap: break-word;
    font-family: 'Orbitron', sans-serif;
}

/* Buttons Layout */
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 15px;
}

/* Button Style */
.btn {
    padding: 18px;
    font-size: 20px;
    border: none;
    border-radius: 15px;
    cursor: pointer;
    background: #1a1a1a;
    color: #ffd700;
    font-weight: 500;
    position: relative;
    overflow: hidden;
    transition: all 0.2s ease;
}

/* Button Ripple Animation */
.btn::after {
    content: "";
    position: absolute;
    width: 100px;
    height: 100px;
    background: rgba(255, 255, 0, 0.3);
    display: block;
    border-radius: 50%;
    transform: scale(0);
    opacity: 0;
    pointer-events: none;
    transition: transform 0.5s, opacity 1s;
}

.btn:active::after {
    transform: scale(3);
    opacity: 1;
    transition: 0s;
}

/* Hover */
.btn:hover {
    background: #333333;
    transform: translateY(-3px);
    box-shadow: 0 5px 15px rgba(255, 255, 0, 0.3);
}

/* Operators */
.operator {
    background: #ffd700;
    color: #000;
    font-weight: 600;
}

.operator:hover {
    background: #e6c200;
}

/* Equal button */
.equal {
    background: #ffea00;
    color: #000;
    grid-row: span 2;
    font-weight: 700;
}

.equal:hover {
    background: #e6d500;
}

/* Zero button */
.zero {
    grid-column: span 2;
}

/* Actions */
.action {
    background: #ff4500;
    color: #fff;
}

.action:hover {
    background: #e03e00;
}

/* Responsive */
@media(max-width:400px) {
    .calculator {
        width: 90%;
    }

    .btn {
        padding: 16px;
        font-size: 18px;
    }

    .output {
        font-size: 28px;
    }
}