* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Helvetica Neue', Arial, sans-serif;
    font-weight: 700;
}

body {
    width: 100%;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background: #c2c2c2;
    padding: 20px;
}

h2 {
    position: absolute;
    top: 20px;
    left: 20px;
    font-size: 24px;
    color: #444;
    letter-spacing: 1px;
}
    
.calculator {
    width: 100%;
    max-width: 380px;
    border: 3px solid #666666; 
    padding: 25px;
    border-radius: 12px; 
    background: #d4d4d4; 
    box-shadow: 15px 15px 30px rgba(0,0,0,0.2);
}

input {
    width: 100%;
    border: 3px solid #555555; 
    padding: 20px;
    margin-bottom: 25px;
    background: #b8c3a9;
    font-family: 'Courier New', Courier, monospace;
    font-size: clamp(30px, 10vw, 45px);
    text-align: right;
    color: #1a1d15;
    border-radius: 4px;
    box-shadow: inset 5px 5px 10px rgba(0,0,0,0.3);
}

input::placeholder {
    color: rgba(0, 0, 0, 0.2);
}

.row {
    display: flex;
    justify-content: space-between;
    margin-bottom: 12px;
}

button {
    border: 1px solid #777777;
    width: clamp(55px, 18vw, 72px); 
    height: clamp(55px, 18vw, 72px);
    cursor: pointer;
    border-radius: 6px;
    background: #e8e8e8;
    color: #333;
    font-size: 20px;
    transition: all 0.05s ease;
    border-bottom: 5px solid #666666; 
}

button:hover {
    background: #ffffff;
    border-color: #444;
}

button:active {
    transform: translateY(4px);
    border-bottom-width: 1px;
    background: #cccccc;
}

/* Functional Utility Keys */
.Operator {
    background-color: #b0b0b0;
    color: #000;
    border-bottom-color: #555555;
}

/* The Classic Accent Button */
.Equal {
    background-color: #b33939; 
    color: white;
    border-color: #7a2828;
    border-bottom-color: #5e1f1f;
}

.Equal:hover {
    background-color: #cd4444;
}