Quick and Easy Sprite –Victorian Rush Hour - Cocos2d-x by Example Beginner's Guide - page 236

} else {
_gameBatchNode->setPositionY ( 0 );
}
4. Make the game more difficult as time goes on by increasing the _player ob-
ject's maximum speed:
if (_terrain->getStartTerrain() &&
_player->getVector().x > 0) {
_speedIncreaseTimer += dt;
if (_speedIncreaseTimer >
_speedIncreaseInterval) {
_speedIncreaseTimer = 0;
_player->setMaxSpeed
(_player->getMaxSpeed() + 4);
}
}
}