I’ve been playing around with an awesome tool called Adobe Scout, which tells you exactly what your Flash games are doing – All the way down to memory allocations, CPU time, and low level GPU calls. It makes fancy graphs of this data, and you can identify where performance sucks, and see exactly what code is causing it. It’s so detailed that running Bullet Heaven 2 for one minute will generate *gigabytes* of data.
I’ve used it to identify a memory leak and a lot of wasted GPU draw calls, and after tidying things up, BH2 runs better than ever. The screenshot shows around 5,000 bullets running at 60fps in 1080p. There's also 80 foes in there.
Obviously my computer is pretty good (but not amazing), but in practice you won’t need this much power. BH2 will rarely need more than 1,000 bullets (much less on easier difficulties), and can be played at 30fps, in a lower resolution. Fancy effects can be disabled too. So the minimum hardware requirements will be tiny – easily low enough to run on older mobile devices.
I’m pretty happy with the performance. :D
Time to get on with actually making the game!
CielComplex
For a moment I thought you were working on a concept SHMUP where you were only allocated a maximum of five thousand bullets and when you run out you're out permanently. But this sounds neat, too.