body {
    margin: 0;
    min-height: 100vh;

    display: flex;
    justify-content: center;
    align-items: center;

    font-family: Arial, sans-serif;
    background: #fff9e6;
    overflow: hidden;
    position: relative;
}

body::before {
    content: "";
    position: fixed;
    inset: 0;

    background-image:
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='96' height='96'%3E%3Ctext x='24' y='24' font-size='28' text-anchor='middle' dominant-baseline='middle' transform='rotate(30 24 24)'%3E%F0%9F%A7%80%3C/text%3E%3Ctext x='72' y='72' font-size='28' text-anchor='middle' dominant-baseline='middle' transform='rotate(30 72 72)'%3E%F0%9F%A7%80%3C/text%3E%3C/svg%3E");

    background-repeat: repeat;
    background-size: 96px 96px;

    filter: blur(2px);
    opacity: 0.35;

    z-index: -1;
}

.container {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 5px 15px rgba(0,0,0,.2);
    width: 350px;
}

h1 {
    text-align: center;
    margin-top: 0;
}

h3 {
    text-align: center;
    color: #aaa;
}

input, select {
    width: 100%;
    padding: 10px;
    font-size: 1rem;
    margin: 10px 0;
    box-sizing: border-box;
}

button {
    width: 100%;
    padding: 12px;
    font-size: 1rem;
    cursor: pointer;
    background: #ffcc33;
    border: none;
    border-radius: 6px;
}

button:hover {
    background: #f2bc00;
}

#swapButton {
margin-bottom: 10px;
}

.result {
    margin-top: 20px;
    font-size: 1.2rem;
    text-align: center;
    font-weight: bold;
}

.mass-input {
    display: flex;
    gap: 8px;
}

.mass-input input {
    width: 100px;
}

.mass-input select {
    flex: 1;
}

small {
    display: block;
    margin-top: 1.2rem;
    font-size: 0.6em;
    text-align: center;
    color: #888;
}