Nice little game! I might be stating the obvious, but it strongly reminded me of Angry Birds :)
There seems to be an issue with window resizing: when resizing after the game has started, part of the elements end up off screen. Conversely, when resizing before the gameplay starts, the elements occupy that much space, which changes the gameplay (and might make the mission impossible?).
Oh! I apologize, I never really paid much attention to resizing :(. Actually the resizing was disabled for me the whole time on Windows :/. Weird.
Thanks for taking the time to review and it playing it. It does feel like Angry Birds, the space one I think. I wanted to make more elaborate missions though and my 8 year old had a ton of ideas on how to improve it further. I will try and continue working on it!
I use EXWM which can force-resize / fullscreen applications, so even if you "disable it", it's just a hint, it never reallyprevent the window manager from going fullscreen.
Keep up with the good work!
In my opinion the most urgent would be sounds to make it more entertaining.
Then the list goes on idefinitely I suppose: traps, moving objects, specials stages with reversed gravity...
