First playable
Well it certainly took its time but I now got the first playable version of the game ready. Currently the controlling happens with the mouse and keyboard (holding keys changes the edit mode and mouse triggers actions). Here is screenshot:

In this image a few bullets have already been shot in a chain reaction and some wall pieces have crumbled. The last bullets are heading towards the last remaining cannon (the point is to start a reaction and use all bullets on all cannons). I’m also planning on adding a simulation time counter and a level specific highscore, so you can optimize each levels time for replay value. Also while testing this proto gameplay, it became apparent the game would be better if some cannons had more than one bullet to fire (so you’d need to make circular reactions).