* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    font-family: 'Segoe UI', sans-serif;
    background: linear-gradient(135deg, #4D8AC8, #6faef0);
}

.calculator {
    backdrop-filter: blur(20px);
    background: rgba(255, 255, 255, 0.15);
    border-radius: 25px;
    padding: 25px;
    width: 340px;
    box-shadow: 
        0 15px 35px rgba(0, 0, 0, 0.2),
        inset 0 0 0 1px rgba(255, 255, 255, 0.2);
    animation: float 3s ease-in-out infinite;
}

@keyframes float {
    0%,100% { transform: translateY(0); }
    50% { transform: translateY(-8px); }
}

.display {
    background: rgba(255, 255, 255, 0.25);
    padding: 18px;
    border-radius: 18px;
    margin-bottom: 20px;
    min-height: 80px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    backdrop-filter: blur(10px);
    box-shadow: inset 0 4px 8px rgba(0,0,0,0.1);
}

#expression {
    font-size: 14px;
    color: #333;
    opacity: 0.8;
    word-wrap: break-word;
}

#result {
    font-size: 30px;
    text-align: right;
    font-weight: bold;
    color: #111;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
}

.btn {
    border: none;
    border-radius: 15px;
    padding: 18px;
    font-size: 18px;
    cursor: pointer;
    transition: all 0.2s ease;
    box-shadow: 0 5px 12px rgba(0,0,0,0.15);
}

.number {
    background: white;
}

.operator {
    background: #b6dcff;
}

.equal {
    grid-column: span 4;
    background: linear-gradient(135deg, #4D8AC8, #2e6da4);
    color: white;
    font-weight: bold;
    font-size: 20px;
    box-shadow: 0 8px 20px rgba(0,0,0,0.3);
}

.btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 10px 18px rgba(0,0,0,0.25);
}

.btn:active {
    transform: scale(0.95);
    box-shadow: 0 3px 8px rgba(0,0,0,0.2);
}

.equal:hover {
    box-shadow: 
        0 0 15px rgba(77, 138, 200, 0.7),
        0 10px 25px rgba(0,0,0,0.3);
}