:root {
    --primary-color: #f5f5f7;
    --secondary-color: #ffffff;
    --accent-color: #007aff;
    --text-color: #1d1d1f;
    --border-color: #d2d2d7;
    --shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
    --radius: 12px;
    --transition: all 0.2s ease;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}

body {
    background-color: var(--primary-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 20px;
}

.calculator-container {
    display: flex;
    max-width: 1200px;
    width: 100%;
    background-color: var(--secondary-color);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    overflow: hidden;
}

.calculator {
    flex: 1;
    padding: 20px;
    display: flex;
    flex-direction: column;
}

.display-container {
    margin-bottom: 20px;
}

.mode-indicator {
    display: flex;
    justify-content: space-between;
    margin-bottom: 10px;
    font-size: 14px;
    color: #86868b;
}

.mode-toggle {
    background: none;
    border: none;
    color: var(--accent-color);
    cursor: pointer;
    font-size: 14px;
    padding: 5px 10px;
    border-radius: 6px;
    transition: var(--transition);
}

.mode-toggle:hover {
    background-color: rgba(0, 122, 255, 0.1);
}

.display {
    background-color: var(--primary-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    padding: 20px;
    text-align: right;
    font-size: 2.5rem;
    min-height: 100px;
    word-wrap: break-word;
    overflow-wrap: break-word;
    margin-bottom: 10px;
}

.expression {
    font-size: 1.2rem;
    color: #86868b;
    min-height: 30px;
    margin-bottom: 10px;
}

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

.button {
    background-color: var(--secondary-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    padding: 15px 10px;
    font-size: 1.3rem;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    justify-content: center;
    align-items: center;
    user-select: none;
}

.button:hover {
    background-color: #f5f5f7;
}

.button:active {
    transform: scale(0.97);
}

.operator {
    background-color: #f2f2f7;
}

.function {
    background-color: #f2f2f7;
    font-size: 1rem;
}

.equals {
    background-color: var(--accent-color);
    color: white;
    grid-column: span 1;
}
.Null-Btn{
    grid-column: span 2;
}

.operator-btn-color{
    background-color: #d3e1ff;
    border: 1px solid var(--border-color);
}

.equals:hover {
    background-color: #0056cc;
}

.clear {
    background-color: #ff3b30;
    color: white;
}

.clear:hover {
    background-color: #d70015;
}

.history {
    width: 300px;
    border-left: 1px solid var(--border-color);
    padding: 20px;
    display: flex;
    flex-direction: column;
}

.history-title {
    font-size: 1.2rem;
    margin-bottom: 15px;
    font-weight: 600;
}

.history-list {
    flex: 1;
    overflow-y: auto;
    max-height: 500px;
}

.history-item {
    padding: 10px;
    border-bottom: 1px solid var(--border-color);
    cursor: pointer;
    transition: var(--transition);
}

.history-item:hover {
    background-color: var(--primary-color);
}

.history-expression {
    font-size: 0.9rem;
    color: #86868b;
}

.history-result {
    font-size: 1.1rem;
    font-weight: 500;
}

.clear-history {
    margin-top: 15px;
    padding: 10px;
    background: none;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    cursor: pointer;
    transition: var(--transition);
}

.clear-history:hover {
    background-color: var(--primary-color);
}

@media (max-width: 900px) {
    .calculator-container {
        flex-direction: column;
        margin-top: 60px;
    }
    
    .history {
        width: 100%;
        border-left: none;
        border-top: 1px solid var(--border-color);
    }
    
    .buttons {
        grid-template-columns: repeat(4, 1fr);
    }
    
    .scientific {
        grid-template-columns: repeat(5, 1fr);
    }
}

@media (max-width: 600px) {
    .buttons {
        grid-template-columns: repeat(3, 1fr);
    }
    
    .scientific {
        grid-template-columns: repeat(4, 1fr);
    }
    
    .display {
        font-size: 2rem;
    }
}