Your screenshot pulled my attention right away. The initial start of the game would have been more inviting with less of a wall of text explaining everything up front. However even with all the explanation it was confusing what was happening. I really like the idea and think it has potential. I would have enjoyed it more if the difficulty progressed a bit. Where you start the players (especially with a second cannon fire) is brutal. Also I wasn't able to aim the cannon, so was confused on that mechanic. Maybe you could have levels where just one mechanic happens at a time to slowly introduce the different parts. Like the first level's goal is to build a tower to surround the ball, then another is to block a single cannon shot, then eventually need to block multiple? Since you don't start the player with a canon (at least I didn't see one) explaining you can aim one doesn't make sense.