You're welcome to download it and check it out - it's all commented. Easier to answer specific questions when you've actually seen it 😂
As for some tips on making your own system more performant:
- Are you object pooling? If not, learn how to do that.
- Do your bullets have rigidbodies? Remove them 😉 rigidbodies are REALLY slow, and you can get away with just having rigidbodies on the colliders on your players/enemies.
- If that's still too slow, you can actually get rid of the rigidbodies on the players/enemies and use Physics2D.OverlapCircle in FixedUpdate - I'd actually recommend the non-allocating version because you want to minimise your garbage collection.
- Check your bullet spawning code for any unnecessary allocations - that's anywhere you've got "new". You can, for example, make a list a member variable and use list.Clear to clear it.
- Check the profiler!! This is a big step, it'll show you where the majority of your performance issues are. You might, for example, be using Linq in your object pooling code to check if there are any available bullets. I was doing that, removing that linq code sped it up about 3x 😅
If that's still not enough, there are some major changes you can make to do it like I do:
- You can rewrite it so all of the movement code is done from one object, and it just updates the positions of the gameobjects rather than the bullet gameobjects themselves having unnecessary monobehaviours attached
- Once you've done that, it's fairly straightforward to use Jobs and multithreading to move the bullets
- Once you've done that, you can try getting rid of Unity's physics entirely, and coding your own circle/circle collision detection as a Job
- Finally, you can remove gameobjects entirely and use command buffers and a custom render pass. This is how I get to 20k bullets at 60fps 😉
If 20k bullets at 60fps isn't enough, you can go full ECS. You probably don't have to do any of the last section, though, the first lot should be plenty to get 1000 on any hardware :)