/* Калькулятор в стиле физического устройства */

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: linear-gradient(135deg, #2c3e50, #3498db);
    font-family: 'Segoe UI', Roboto, 'Helvetica Neue', sans-serif;
}

.calculator {
    width: 320px;
    background: #1e1e1e;
    border-radius: 20px;
    box-shadow: 0 20px 50px rgba(0,0,0,0.5), inset 0 1px 0 rgba(255,255,255,0.1);
    overflow: hidden;
    padding: 15px;
}

.calculator__display {
    width: 100%;
    height: 70px;
    border: none;
    background: #c8d6b7;
    border-radius: 10px;
    margin-bottom: 15px;
    padding: 10px 15px;
    font-size: 28px;
    text-align: right;
    color: #1a1a1a;
    font-family: 'Courier New', Courier, monospace;
    box-shadow: inset 0 2px 5px rgba(0,0,0,0.3);
    outline: none;
}

.calculator__buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
}

.btn {
    height: 55px;
    font-size: 20px;
    border: none;
    border-radius: 10px;
    background: #333;
    color: #fff;
    cursor: pointer;
    box-shadow: 0 4px 0 #1a1a1a, 0 6px 10px rgba(0,0,0,0.3);
    transition: all 0.08s ease;
    user-select: none;
}

.btn:active {
    transform: translateY(3px);
    box-shadow: 0 1px 0 #1a1a1a, 0 3px 6px rgba(0,0,0,0.3);
}

.btn--digit {
    background: #424242;
}

.btn--zero {
    grid-column: span 2;
}

.btn--operator {
    background: #f39c12;
    color: #fff;
    font-weight: bold;
}

.btn--operator:active {
    background: #e67e22;
}

.btn--clear {
    background: #c0392b;
    color: #fff;
    font-weight: bold;
}

.btn--clear:active {
    background: #a93226;
}

.btn--equals {
    background: #27ae60;
    color: #fff;
    font-weight: bold;
}

.btn--equals:active {
    background: #1e8449;
}

.btn--bracket {
    background: #555;
}

.btn--dot {
    background: #555;
}