* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
 
body {
    min-height: 100vh;
    background: linear-gradient(135deg, #667eea, #764ba2);
    font-family: 'Segoe UI', sans-serif;
 
    display: flex;
    justify-content: center;
    align-items: center;
}
 
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    padding: 20px 28px;
    z-index: 10;
}
 
.logo {
    display: inline-block;
    padding: 8px 18px;
    font-size: 22px;
    font-weight: 800;
    letter-spacing: 1px;
    color: #4f46e5;
    background: #ffffff;
    border-radius: 14px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.25);
}
 
.calculator {
    width: 340px;
    padding: 22px;
    background: #ffffff;
    border-radius: 18px;
    box-shadow: 0 25px 50px rgba(0,0,0,0.3);
 
    margin-top: 80px; /* prevents navbar overlap */
}
 
#display {
    width: 100%;
    height: 64px;
    font-size: 26px;
    text-align: right;
    padding: 12px;
    margin-bottom: 18px;
    border-radius: 12px;
    border: none;
    background: #f3f4f6;
}
 
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-auto-rows: 56px;
    gap: 14px;
}
 
button {
    height: 56px;
    font-size: 18px;
    font-weight: 600;
    border: none;
    border-radius: 14px;
    cursor: pointer;
    background: #e5e7eb;
    transition: all 0.15s ease;
}
 
button:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 16px rgba(0,0,0,0.2);
}
 
button:active {
    transform: scale(0.95);
}
 
.operator {
    background: linear-gradient(135deg, #ff9a9e, #fad0c4);
}
 
.control {
    background: linear-gradient(135deg, #fbc2eb, #a6c1ee);
}
 
.equals {
    background: linear-gradient(135deg, #43e97b, #38f9d7);
    color: #000;
 
    grid-row: span 3;
    height: 100%;
}
 
.zero {
    grid-column: span 2;
}