* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background: linear-gradient(120deg, #a1c4fd, #c2e9fb);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

.container {
    width: 100%;
    max-width: 400px;
    padding: 20px;
}

h1 {
    color: #333;
    text-align: center;
    margin-bottom: 20px;
    text-shadow: 1px 1px 2px rgba(0, 0, 0, 0.1);
}

.calculator {
    background-color: white;
    border-radius: 10px;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
    padding: 30px;
}

.input-group {
    margin-bottom: 15px;
}

.input-group input {
    width: 100%;
    padding: 12px;
    border: 1px solid #ddd;
    border-radius: 5px;
    font-size: 16px;
    transition: border 0.3s;
}

.input-group input:focus {
    outline: none;
    border-color: #a1c4fd;
}

.operation-group {
    display: flex;
    justify-content: space-between;
    margin-bottom: 15px;
}

.op-btn {
    flex: 1;
    padding: 10px;
    margin: 0 5px;
    border: none;
    border-radius: 5px;
    background-color: #f0f0f0;
    font-size: 18px;
    cursor: pointer;
    transition: all 0.3s;
}

.op-btn:first-child {
    margin-left: 0;
}

.op-btn:last-child {
    margin-right: 0;
}

.op-btn:hover {
    background-color: #e0e0e0;
}

.op-btn.active {
    background-color: #a1c4fd;
    color: white;
}

.calculate-btn {
    width: 100%;
    padding: 12px;
    background-color: #4CAF50;
    color: white;
    border: none;
    border-radius: 5px;
    font-size: 16px;
    cursor: pointer;
    transition: background-color 0.3s;
}

.calculate-btn:hover {
    background-color: #45a049;
}

.result {
    margin-top: 20px;
    padding: 15px;
    background-color: #f9f9f9;
    border-radius: 5px;
    text-align: center;
    min-height: 60px;
}

.result p {
    font-size: 20px;
    color: #333;
}

.calculation {
    font-size: 14px;
    color: #666;
    margin-top: 5px;
}