Hi I`m trying to design a shooting game. The shoot-em-up type of game. I wanted to know if there are any resources on making this kind of shooter game. Like what kind of bullets or special attack used in these kinds of game? how will the boss move and if the boss has just a certain weakness or something. Any advice or suggestions are greatly appreciated.

One important aspect that needs a lot of attention is something that shouldn't be overlooked for any type of game where a specific action is focused on (punching in a fighting game, kicking in a football game, killing in a zombie game). The events that occur because of this action need to provide a high sense of satisfaction. For a fighting game, this could come in the form of crunching bone sound effects on hard hits, for example.

For a shooter, most of it will come in the form of sound effects, particles, and explosions. The particles and sound effects of explosions are extremely important. If you can, make explosions dynamic and unpredictable so that each one varies wildly. Allow them to actually influence the game, such as having pieces of craft go flying off in different directions, allowing the pieces to be further destroyed or to impact and damage other enemies. Screen vibration that occurs on hard impacts can be good (let this be disabled in options). Generally, any kind of detail that occurs when you destroy things will be a plus, and will help make destroying things feel good.

Personally, if done well enough, I believe a game can thrive decently on this concept alone, even if it is too easy or has a terrible plot. Games like pinball rely on it almost exclusively. Anyway, that's my one tip. Good luck.