.collatz-btn {
    width: 100%;
    padding: 10px 0;
    font-size: 16px;
    margin: 10px 0;
    display: block;
    border-radius: 10px;
    box-shadow: 0 4px 12px rgba(40, 100, 180, 0.2);
    background: #2972c4;
    color: white;
    font-weight: bold;
    border: none;
    cursor: pointer;
    text-align: center;
}

.collatz-btn:hover, .collatz-btn:focus {
    box-shadow: 0 8px 24px rgba(30, 70, 160, 0.35);
    background: #1968c9;
}

.collatz-q-btn {
    width: 100%;
    padding: 14px 0;
    font-size: 18px;
    margin: 8px 0;
    border-radius: 12px;
    box-shadow: 0 2px 6px rgba(120, 120, 140, 0.10);
    background: #f2f6fa;
    color: #134080;
    font-weight: 500;
    border: 1px solid #bcd;
    cursor: pointer;
    text-align: center;
    transition: box-shadow 0.2s, background 0.1s;
}

.collatz-q-btn:hover, .collatz-q-btn:focus {
    background: #e2edfb;
    box-shadow: 0 4px 12px rgba(40, 100, 180, 0.13);
    color: #1a73e8;
}

html, body {
    height: 100%;
    margin: 0;
    padding: 0;
}

#main-container {
    min-height: 100%;
    display: flex;
    flex-direction: column;
}

.content {
    flex: 1;
}