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


#birdGameCanvas {
    position: fixed;
    inset: 0;
    width: 100vw;
    height: 100dvh;
    display: none;
    pointer-events: none;
    z-index: 100; /* ← cao hơn header (99) là đủ */
}

#bird-game-overlay {
    position: fixed;
    inset: 0;
    width: 100vw;
    height: 100dvh;
    background: transparent;
    z-index: 101; /* ← cao hơn canvas */
    display: none;
    pointer-events: none;
}

#bird-game-back {
    position: absolute;
    top: 15px;
    left: 15px;
    z-index: 102;
    padding: 12px 20px;
    border: none;
    border-radius: 8px;
    background: #fff;
    cursor: pointer;
    pointer-events: auto;
}

#bird-game-replay {
    position: absolute;
    top: 15px;
    right: 15px;
    z-index: 102;
    padding: 12px 20px;
    border: none;
    border-radius: 8px;
    background: #fff;
    color: black;
    cursor: pointer;
    pointer-events: auto;
}

#bird-game-play {
    padding: 15px 30px;
    font-size: 20px;
    cursor: pointer;
}