/* Desain Umum */
body {
    font-family: 'Arial', sans-serif;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-color: #f5f5f5;
}

/* Header */
header {
    width: 100%;
    text-align: center;
    padding: 20px;
    background-color: #4CAF50;
    color: #fff;
    font-size: 28px;
    font-weight: bold;
    border-radius: 8px 8px 0 0;
}

/* Kalkulator */
.calculator {
    width: 350px;
    padding: 30px;
    background-color: #fff;
    border-radius: 15px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    transition: background-color 0.3s ease;
}

/* Display */
#display {
    width: 100%;
    padding: 15px;
    margin-bottom: 20px;
    text-align: right;
    font-size: 32px;
    border: 2px solid #ccc;
    border-radius: 8px;
    background-color: #f8f8f8;
    color: #333;
    transition: color 0.3s ease, background-color 0.3s ease;
}

/* Pesan Error */
.error-message {
    color: #e74c3c;
    font-size: 18px;
    text-align: center;
    margin-bottom: 10px;
}

/* Tombol */
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

.btn {
    padding: 20px;
    font-size: 22px;
    border: 1px solid #ccc;
    background-color: #e0e0e0;
    cursor: pointer;
    border-radius: 8px;
    transition: all 0.3s ease;
}

.btn:hover {
    background-color: #d0d0d0;
}

.btn:active {
    background-color: #b0b0b0;
}

.btn:focus {
    outline: none;
}

button:disabled {
    background-color: #f5f5f5;
    cursor: not-allowed;
}

/* Mode Gelap */
body.dark-mode {
    background-color: #333;
}

.calculator.dark-mode {
    background-color: #444;
}

#display.dark-mode {
    background-color: #222;
    color: #fff;
}

button.dark-mode {
    background-color: #555;
    color: #fff;
}

button.dark-mode:hover {
    background-color: #666;
}

/* Toggle Tema */
.theme-toggle {
    margin-top: 20px;
    text-align: center;
}

/* Footer */
footer {
    width: 100%;
    text-align: center;
    padding: 10px;
    background-color: #4CAF50;
    color: #fff;
    font-size: 16px;
    margin-top: 20px;
    border-radius: 0 0 8px 8px;
}