html, body {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    background: #000;
    overflow: hidden;
    font-family: sans-serif;
    color: #fff;
    -webkit-tap-highlight-color: transparent;
    -webkit-user-select: none;
    user-select: none;
    touch-action: none;
    overscroll-behavior: none;
}

#game-container {
    display: flex;
    justify-content: center;
    align-items: center;
    width: 100%;
    height: 100vh;
    height: 100dvh;
}

#game-container canvas {
    display: block;
    image-rendering: auto;
    -ms-interpolation-mode: bicubic;
}

#rotate-hint {
    position: fixed;
    inset: 0;
    background: #000;
    color: #fff;
    z-index: 9999;
    display: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
    font-size: 22px;
    padding: 24px;
}
#rotate-hint .rotate-icon {
    font-size: 80px;
    animation: spin 2s ease-in-out infinite;
    margin-bottom: 24px;
}
#rotate-hint .rotate-sub {
    font-size: 14px;
    color: #aaa;
    margin-top: 12px;
}
@keyframes spin {
    0%, 100% { transform: rotate(0deg); }
    50%      { transform: rotate(90deg); }
}

@media (orientation: portrait) and (max-width: 900px) {
    #rotate-hint { display: flex; }
}