/* Root variables for themes */
:root {
    --bg-color: #f4f4f4;
    --text-color: #333;
    --display-bg: #fff;
    --button-bg: #e0e0e0;
    --button-hover: #ccc;
    --scientific-bg: #a8dadc;
    --operator-bg: #f7cac9;
    --memory-bg: #ffeaa7;
    --control-bg: #d3d3d3;
    --shadow: rgba(0, 0, 0, 0.1);
    --font-family: 'Arial', sans-serif;
}

.dark-mode {
    --bg-color: #1e1e1e;
    --text-color: #ddd;
    --display-bg: #333;
    --button-bg: #444;
    --button-hover: #555;
    --scientific-bg: #457b9d;
    --operator-bg: #e63946;
    --memory-bg: #ffaf40;
    --control-bg: #6c757d;
    --shadow: rgba(0, 0, 0, 0.5);
}

/* General styles */
body {
    font-family: var(--font-family);
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    padding: 20px;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    transition: background-color 0.3s, color 0.3s;
}

.calculator-container {
    max-width: 600px;
    width: 100%;
}

.calculator-title {
    text-align: center;
    margin-bottom: 20px;
    font-size: 24px;
}

.calculator {
    background-color: var(--display-bg);
    border-radius: 10px;
    box-shadow: 0 4px 8px var(--shadow);
    padding: 20px;
    display: grid;
    grid-template-columns: 3fr 1fr;
    gap: 20px;
    transition: background-color 0.3s;
}

.display {
    grid-column: 1 / -1;
    background-color: var(--bg-color);
    border-radius: 5px;
    padding: 10px;
    margin-bottom: 10px;
    text-align: right;
    font-size: 24px;
    min-height: 60px;
}

.input {
    color: #888;
    font-size: 18px;
}

.output {
    font-size: 32px;
    font-weight: bold;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 10px;
}

.btn {
    background-color: var(--button-bg);
    border: none;
    border-radius: 5px;
    padding: 15px;
    font-size: 18px;
    cursor: pointer;
    transition: background-color 0.2s, transform 0.1s;
    color: var(--text-color);
}

.btn:hover {
    background-color: var(--button-hover);
}

.btn:active {
    transform: scale(0.98);
}

.scientific {
    background-color: var(--scientific-bg);
}

.operator {
    background-color: var(--operator-bg);
}

.memory {
    background-color: var(--memory-bg);
    grid-column: span 1;
}

.control {
    background-color: var(--control-bg);
}

.theme-toggle {
    background-color: var(--control-bg);
    font-size: 20px;
}

.history {
    background-color: var(--bg-color);
    border-radius: 5px;
    padding: 10px;
    max-height: 400px;
    overflow-y: auto;
    transition: background-color 0.3s;
}

.history h2 {
    font-size: 16px;
    margin: 0 0 10px;
}

.history-log div {
    margin-bottom: 10px;
    text-align: right;
    border-bottom: 1px solid var(--shadow);
    padding-bottom: 5px;
}

.history-log .calc {
    color: #888;
    font-size: 14px;
}

.history-log .result {
    font-weight: bold;
    font-size: 16px;
}

/* Responsive design */
@media (max-width: 600px) {
    .calculator {
        grid-template-columns: 1fr;
    }

    .history {
        max-height: 200px;
        margin-top: 20px;
    }

    .buttons {
        grid-template-columns: repeat(5, 1fr);
    }

    .btn {
        padding: 10px;
        font-size: 16px;
    }

    .display {
        font-size: 20px;
    }

    .output {
        font-size: 28px;
    }
}

/* High contrast and accessibility */
.btn {
    color: contrast(var(--text-color), #000, #fff); /* Pseudo for high contrast */
}