body {
    font-family: "Segoe UI", Arial, sans-serif;
    margin: 0;
    background: #0d1117;
    color: #e6e6e6;
}

header {
    background: #0d1117;
    color: #C4D6B0;
    text-align: center;
    padding: 40px 20px;
    border-bottom: 3px solid #1f2933;
}

header h1 {
    margin: 0;
    font-size: 42px;
}

.subtitle {
    margin-top: 5px;
    font-size: 20px;
    opacity: 0.9;
}

.card {
    background: #1f2933;
    margin: 20px;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 3px 10px rgba(0,0,0,0.4);
}

.card h2 {
    margin-top: 0;
    color: #C4D6B0;
}

.btn {
    display: inline-block;
    background: #C4D6B0;
    color: #1f2933;
    padding: 12px 24px;
    border-radius: 8px;
    text-decoration: none;
    font-size: 18px;
    margin-top: 10px;
    transition: 0.25s;
}

.btn:hover {
    background: #ffffff;
    color: #1f2933;
}

footer {
    text-align: center;
    margin: 40px 0;
}

.back {
    color: #C4D6B0;
    font-size: 18px;
    text-decoration: none;
}

.back:hover {
    text-decoration: underline;
}

.center-button {
    text-align: center;
    margin: 40px 0;
}

.main-btn {
    background: #C4D6B0;
    color: #1f2933;
    padding: 14px 32px;
    font-size: 22px;
    border-radius: 10px;
    text-decoration: none;
    font-weight: bold;
    transition: 0.25s;
    box-shadow: 0 4px 12px rgba(0,0,0,0.4);
}

.main-btn:hover {
    background: #ffffff;
    color: #1f2933;
}

/* 
Calculator
*/

.calculator {
    background-color: #35393d;
    margin: 20px;
    padding: 20px;
    border-radius: 10px;

    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-template-rows: 100px auto; /* erste Zeile groß, Rest flexibel */
    gap: 10px;
}

#display {
    grid-column: span 4; /* nimmt alle 4 Spalten ein */
    background-color: #222;
    color: white;
    font-size: 32px;
    padding: 20px;
    border-radius: 10px;
}




.number,
.operator,
.sum,
.point {
    width: 100%;
    height: 80px;
    background-color: #b9b9b9;
    color: white;
    border: none;
    border-radius: 10px;
    margin: 5px;
    font-size: 24px;
    cursor: pointer;
}

.operator {
    background-color: rgb(40, 93, 129);
}

.sum {
    background-color: rgb(51, 30, 93);
}