Ah, it's autodetected. This is cool. I compared the speed in two emulator-windows at the same time, by emulating a Amiga500 in one window and a Amiga1200 in the other and the game is indeed playable on the A500, in this 25FPS mode. Sadly it does not run in real fullspeed, it seems, because it plays a bit faster on the A1200 (and of course more smoothly, because no frames need to be skipped, on the AGA machine). But nevertheless, like i already wrote, it's at least playable on the A500 now, so i think this 25FPS mode (every second frame skipped), was a good idea anyway.
One last question about this, because this frameskipping thing is interesting. I can remember, that you once wrote me on the webpage of your "Galaga 500" game, that this game also runs at a 25FPS-mode on A500 machines, but that it's still too slow on non-AGA-Amigas, because some of the code still has to run at 50fps (or something like that). But would it be possible, to give "Galaga500" an auto-frameskip mode for A500 machines, or would the frame jumps in the gameplay then be too large, making it run too choppy or jerky? Maybe it would be worth a try? Or perhaps, if that's not possible, an alternative mode, in which only every third frame is displayed and maybe the game could only then switch to this, when the A500 could not hold the fullspeed in the 25FPS mode anymore (e.g. too many opponents on the screen at the same time, etc) and otherwise run the game in 25FPS mode (as it is now)? Perhaps it could then maintain the full speed of the Arcade version on A500 machines then? What do you think?