I think this would be something for Misery and I think for other people on this forum as well.
Evil factory can be best described as a mix of Bomberman (the classic one) and Bullet Hell fights. Every level is a boss fight in this game and every boss has set attack patterns that you have to examine, analyze and learn to dodge. The first boss has a very simple pattern to understand but the game gets harder and harder with each boss. The game is segmented in multiple chapters and at the end of each chapter a "super boss" waits for you that is even stronger than the normal bosses you fight.
To defeat the boss you can plant dynamite (like bombs) on the ground and lure your enemy on to it. Later you get other explosives and secondary weapons. Explosives have unlimited use, secondary weapons can only be used for a limited time per level.
You can also upgrade existant weapons if you find the required blueprints for them.
The game is entirely free to play but has a "action point" system that allows you only to play a set amount of levels until you have to refresh (over time) new action points. Or you can simply pay a small microtransaction and remove action points entirely (you can consider this the "full version" of the game).
I think for a free game this is really cool and while it may not appease the hardcore bullet hell players, it is a nice casual experience with cool looking art and bosses. Also some kind of story that you can skip if you want to.