html, body {
    height: 100%;
    margin: 0;
    background: linear-gradient(180deg, black, darkslategrey);
    font-family: system-ui, -apple-system, Segoe UI, Roboto, "Helvetica Neue", Arial;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    touch-action: manipulation;
}

.wrap {
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    user-select: none;
}

.number {
    font-weight: 700;
    color: #fff;
    /* large, responsive size */
    font-size: clamp(64px, 20vw, 320px);
    line-height: 1;
    transition: transform 120ms cubic-bezier(.2, .9, .3, 1);
    will-change: transform;
    -webkit-tap-highlight-color: transparent;
    text-shadow: 0 6px 30px rgba(0, 0, 0, 0.6);
}

.pop {
    transform: scale(1.06);
}

/* small instruction at bottom (subtle) */
.hint {
    position: fixed;
    left: 50%;
    bottom: 18px;
    transform: translateX(-50%);
    color: rgba(255, 255, 255, 0.65);
    font-size: 13px;
    font-weight: 500;
    letter-spacing: 0.02em;
    backdrop-filter: blur(6px);
    padding: 6px 10px;
    border-radius: 999px;
}