body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #f0f0f0;
}

#app {
    max-width: 400px;
    width: 100%;
    margin: 20px;
}

header {
    text-align: center;
    margin-bottom: 20px;
}

.toggles {
    margin-top: 10px;
}

.toggles button {
    margin: 0 5px;
    padding: 5px 10px;
    background-color: #007bff;
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
}

.calculator {
    background-color: white;
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(0,0,0,0.1);
    padding: 20px;
}

.display {
    margin-bottom: 20px;
}

#display {
    width: 100%;
    height: 50px;
    font-size: 24px;
    text-align: right;
    border: 1px solid #ccc;
    border-radius: 5px;
    padding: 10px;
    box-sizing: border-box;
}

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

.btn {
    height: 50px;
    font-size: 18px;
    border: 1px solid #ccc;
    border-radius: 5px;
    background-color: #fff;
    cursor: pointer;
    transition: background-color 0.2s;
}

.btn:hover {
    background-color: #e9e9e9;
}

.operator {
    background-color: #f8f9fa;
}

.equal {
    background-color: #28a745;
    color: white;
}

.equal:hover {
    background-color: #218838;
}

.scientific-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    margin-top: 10px;
}

.memory-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    margin-top: 10px;
}

.history-panel {
    margin-top: 20px;
    background-color: #f8f9fa;
    padding: 10px;
    border-radius: 5px;
}

#history-list {
    list-style: none;
    padding: 0;
    max-height: 200px;
    overflow-y: auto;
}

#history-list li {
    padding: 5px 0;
    border-bottom: 1px solid #ccc;
}

footer {
    text-align: center;
    margin-top: 20px;
    font-size: 14px;
    color: #666;
}