It's an interesting concept, but you could improve upon it in many ways, like enemy variety, better graphics, more complex combat, etc. It's a cool idea, but it just gets boring after a while because of the lack of content, and the limited ammo's a turnoff, too, considering this is an arcade shooter. I'd like to see what you do with something like this in the future, but this version isn't all that good. As an experiment it works, as a game it flops. But keep going with this, you could turn this idea into something really cool!

This game fails hard as it is. You should do away with the limited ammo / passing ammo thing. Pursuing a new idea just because it has never been done before isn't a good thing if it's a bad idea that doesn't work. The way it is, you have a choice between keeping the 2 ships at the same horizontal level and having the ammo build up by 1 every time they take out an enemy together, since they regenerate a round in ammo when they hit an enemy yet the shot continues to the other player, until one of them gets shot by the identical falling enemies, or giving up on one of the players shooting at all and just leaving it down below, while the other one goes up and takes them out without missing a shot, but with the advantage of presenting a smaller target for the falling triangles to hit (and thereby end the game immediately). Or more optimally, spending 10% of the time doing the first method and 90% of the time the second method to regenerate ammo as needed. Either way, it makes for a very boring game. I got to 40 before being shot with one of them and then that was that. Maybe a more complicated dynamic for the players in response to dying. Like rather than the game being over immediately, 1 shot and you're done, maybe that player is gone, but if the other player shoots 20 enemies alone the other player comes back. And some better enemies, rather than the slowly falling triangles that never vary in speed and just shoot to the side. This might actually be slightly better with 2 people, they might be able to work out a technique that minimizes the risks. I didn't notice, does each individual enemy only shoot to one side or can it switch? The side that knows it's safe could be the one to go after each one for instance. But it's still not very engaging and it runs out of what little interestingness value it had quickly. If this was an atari 2600 game, it would quite possibly be remembered as the worst game ever. Worse than ET. If it was left like this.

Really a solid simple game, I don't see many ways to improve on the formula besides adding a variety of enemies.