Don't undersell it. The game is playable in a browser. The graphics are just blocks, the aliens don't return fire. There are no bunkers. The aliens change colors when they descend to a new level (whoops). But for less than 60 seconds of effort it does include the aliens (who do properly go all the way to the edges, so the strategy of shooting the sides off of the formation still works--not every implementation gets that part right), and it does detect when you have won the game. The tank and the bullets work, and it even maintains the limit on the number of bullets you can have in the air at once. However, the bullets are not destroyed by the aliens so a single shot can wipe out half of a column. It also doesn't have the formation speed up as you destroy the aliens.

So it is severely underbaked but the base gameplay is there. Roughly what you would expect out of a LLM given only the high level objective. I would expect an hour or so of vibe coding would probably result in something reasonably complete before you started bumping up into the context window. I'm honestly kind of impressed that it worked at all given the minuscule amount of human input that went into that prompt.