* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
}

body {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    background: #f4f1ea;
    padding: 20px;
}

.back-button {
    text-decoration: none;
    padding: 12px 20px;
    border: none;
    background: #e8e4d9;
    color: #5c4b3c;
    font-weight: 500;
    border-radius: 8px;
    margin-bottom: 20px;
    font-size: 1.1rem;
    transition: all 0.3s ease;
    box-shadow: 0 2px 4px rgba(92, 75, 60, 0.1);
}

.back-button:hover {
    background: #dcd8cd;
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(92, 75, 60, 0.15);
}

.calculator {
    padding: 25px;
    border-radius: 16px;
    background: linear-gradient(145deg, #e8e4d9, #f4f1ea);
    box-shadow: 0 8px 32px rgba(92, 75, 60, 0.15);
    max-width: 400px;
    width: 100%;
}

.display {
    padding: 20px;
    margin-bottom: 25px;
    border-radius: 12px;
    background: #fff;
    box-shadow: inset 0 2px 4px rgba(92, 75, 60, 0.1);
    text-align: right;
    min-height: 100px;
}

.previous-operand {
    font-size: 1.1rem;
    color: #8b7355;
    min-height: 24px;
}

.current-operand {
    font-size: 2.2rem;
    color: #5c4b3c;
    margin-top: 8px;
}

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

button {
    padding: 20px;
    font-size: 1.25rem;
    border: none;
    background: #f4f1ea;
    color: #5c4b3c;
    cursor: pointer;
    border-radius: 8px;
    transition: all 0.3s ease;
    box-shadow: 0 2px 4px rgba(92, 75, 60, 0.1);
}

button:hover {
    background: #e8e4d9;
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(92, 75, 60, 0.15);
}

button:active {
    transform: translateY(0);
    box-shadow: 0 1px 2px rgba(92, 75, 60, 0.1);
}

button[data-operation] {
    background: #dcd8cd;
    color: #3c2f1b;
}

button[data-equals] {
    background: #8b7355;
    color: #fff;
    grid-column: span 2;
}

button[data-all-clear],
button[data-delete] {
    background: #c9bfae;
    color: #3c2f1b;
}