* {
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background-color: #f4f6f8;
    margin: 0;
    padding: 20px;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 90vh;
}

.kalkulator {
    width: 100%;
    max-width: 320px;
    background: #ffffff;
    padding: 12px;
    border-radius: 12px;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
    border: 1px solid #e2e8f0;
}

#layar {
    width: 100%;
    height: 65px;
    border: 1px solid #cbd5e1;
    border-radius: 8px;
    font-size: 28px;
    font-weight: 600;
    color: #1e293b;
    padding: 10px 14px;
    text-align: right;
    outline: none;
    background-color: #f8fafc;
    margin-bottom: 12px;
}

.container-tombol {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}

.tombol {
    display: flex;
    width: calc(25% - 4.5px);
    font-size: 20px;
    color: #334155;
    font-weight: 600;
    height: 60px;
    border: 1px solid #e2e8f0;
    border-radius: 8px;
    justify-content: center;
    align-items: center;
    background: #f1f5f9;
    cursor: pointer;
    user-select: none;
    transition: background 0.15s ease, transform 0.05s ease;
}

.tombol:hover {
    background: #e2e8f0;
}

.tombol:active {
    transform: scale(0.96);
}

#nol {
    width: calc(75% - 1.5px);
    flex-grow: 1;
}

.operator {
    background: #e2e8f0;
    color: #0f172a;
}

.operator:hover {
    background: #cbd5e1;
}

#hitung {
    background: #ff9800;
    color: #ffffff;
    border-color: #f57c00;
    width: calc(25% - 4.5px);
}

#hitung:hover {
    background: #f57c00;
}