:root {
    --bg-start: #547dcb;
    --bg-end: #4b74c1;
    --button: #f5842d;
    --button-hover: #ff9a49;
    --button-shadow: rgba(28, 47, 93, 0.22);
    --text: #ffffff;
    --hint: rgba(255, 255, 255, 0.72);
}

* {
    box-sizing: border-box;
}

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

body {
    font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
    background:
        radial-gradient(circle at top, rgba(255, 255, 255, 0.12), transparent 35%),
        linear-gradient(180deg, var(--bg-start), var(--bg-end));
}

.version-selector {
    min-height: 100vh;
    display: grid;
    place-items: center;
    padding: 24px;
}

.panel {
    width: min(100%, 340px);
    display: grid;
    gap: 18px;
    justify-items: center;
}

.version-button {
    width: 100%;
    max-width: 260px;
    padding: 18px 28px;
    border-radius: 12px;

    font-size: 18px;
    font-weight: 900;
    letter-spacing: 0.1em;

    background: var(--button);
    color: #fff;

    text-align: center;
    text-decoration: none;

    box-shadow: 0 14px 28px var(--button-shadow);

    transition: all .2s ease;
}

.version-button:hover,
.version-button:focus-visible {
    background: var(--button-hover);
    transform: translateY(-2px);
    box-shadow: 0 16px 28px rgba(28, 47, 93, 0.28);
}

.version-button:focus-visible {
    outline: 3px solid rgba(255, 255, 255, 0.42);
    outline-offset: 3px;
}

.helper-text {
    margin: 8px 0 0;
    text-align: center;
    font-size: 0.82rem;
    line-height: 1.5;
    color: var(--hint);
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

@media (max-width: 480px) {
    .panel {
        gap: 14px;
    }

    .version-button {
        max-width: 100%;
    }

    .helper-text {
        font-size: 0.76rem;
    }
}

.btn-danger {
    background: #e53935;
}

.btn-danger:hover {
    background: #ff4d4d;
}

.btn-success {
    background: #2e7d32;
}

.btn-success:hover {
    background: #43a047;
}