Thank for the early review. Since then I went ahead and added some player aid to the game description.
Clicking once on the ships should be enough, but the battle is not started based on collision, instead it auto-starts when the player ship catches up to the enemy. So if you choose a ship, click on it, and wait, it will most likely start the battle, unless the ship gets away.
I had a lot more in mind for this game: random generated ship layouts, different loots that can be crafted into different upgrades, a second zone, with sheep ships with more health and deadlier weapons, and I was also dreaming about an on board real time combat. And of course, sounds, music, special effect, maybe voice-over.
I'll definitely continue development after the jam, even if I won't add all the above mentioned featured. So if you liked it, stay tuned.