.calculator {max-width: 400px;margin: 40px auto;border-radius: 12px;box-shadow: 0 0 10px rgba(0,0,0,.1);padding: 20px;background: #fff;font-family: Arial,sans-serif;}
.display {display: flex;flex-direction: column;gap: 10px;margin-bottom: 20px;}
#calc-display {width: 100%;font-size: 1.5rem;padding: 10px;border-radius: 6px;border: 1px solid #ccc;text-align: right;}
.mode-toggle {display: flex;justify-content: space-between;font-size: .9rem;}
.buttons {display: grid;grid-template-columns: repeat(5,1fr);gap: 10px;}
button {padding: 15px;font-size: 1rem;border: none;border-radius: 8px;background-color: #f0f0f0;cursor: pointer;transition: background-color .2s ease,transform .1s ease;box-shadow: 0 2px 5px rgba(0,0,0,.1);}
button:hover {background-color: #d0e8ff;transform: scale(1.03);}
button.num-key {background-color: #e8f9e9;}
button.num-key:hover {background-color: #c7f5c7;}
button.equal-btn {background-color: #2196f3;color: #fff;}
button.equal-btn:hover {background-color: #1976d2;}