I've started on implementing some turrets to shoot at the player's rocket.
This is a chance to use my aiming math (here's another explanation from Scott Lembcke with graphs instead of equations). So far I have the turrets aiming without regard for acceleration of any kind. I'm searching for a combination of parameters that will make the player react while still leaving them enough time to do so. I think I will want to make the turrets smart enough to take into account the rocket's acceleration; otherwise it's too easy to dodge them by just flying through with your engine blazing. Maybe there will be different kinds of turrets with different target-leading algorithms; if they're clearly visually different it could be interesting. One would aim to hit the rocket without considering velocity or acceleration; one would aim considering only velocity; and one would aim considering both velocity and acceleration.
Having some additional projectiles is making me realize that my gravity is not very strong. The bullets don't arc much. I don't remember but I think I originally sized the gravity so it would be similar to Earth gravity based on the rough size of the rocket. Just looking at how long it takes to fall its own height when starting from rest (at sea level). After I have the turrets basically working I think I'll do a round of gravity strength experiments. Of course the rocket engine will have to be scaled accordingly; it needs to be able to deliver greater acceleration than gravity at “sea level” (where the gravity is strongest). Scaling gravity up might speed up the gameplay which could be interesting. I have it in my mind to add on-foot movement (a la Star Guard) and wheeled vehicle movement, so the gravity will need to feel OK for those too.
The projectiles need a lot of extra work. They need to go away upon intersection with the rocket, and they need to deliver an impulse and some damage. At the moment they are regular colliding bodies, so they do deliver some impulse and damage but I'd like it to be arbitrarily tunable. I think I will have the bullets “fade out” over time so they deliver less damage as they age, before disappearing entirely.
The turrets need to have their range of motion clamped so they can't shoot into the ground.
I'm weighing whether it's worth it to have my own version of the physics library (I translated it from C to C++) and keep porting vendor drops from the original, or whether I should just write the necessary shims to connect up the C library to my vector class and what-not so I can use it directly. I'm sort of inclining toward the latter. I'm also looking at Box2D again, although I haven't quite figured out how I would translate my collision shapes to their model. They have a maximum of eight vertices per convex shape, I think, so I'd need to make a bunch of shapes to represent my curved surfaces (my game's all about curved surfaces).