If you haven't played TxK on the Vita, or if you've been holding off on it for whatever reason, you might want to consider getting it as soon as possible. Atari has deemed that
they want to make money off of someone the game is too similar to Tempest, ordering that the game be pulled from PSN and that no other ports be made, threatening legal action.
The game is currently $10 on PSN, if you're interested. Again, it may not last long at this point as the creator of the game doesn't have the budget to handle a legal battle with something like Atari.