Nice game! The core game loop is interesting and the blackhole catching up to the player definitely creates tension and has potential for things like scoring systems based off of completion speed. A few things to improve should you expand upon the game would probably it's performance (I was only able to get about 20FPS average) and maybe a block indicator that lets you know where exactly the block you are going to place would go. One interesting quirk in the game's design I found is that since you can place and regain blocks immediately, you can jump, remove the block under you, and then place a block under you afterward. You could either remove this mechanic or use it as a factor in future levels, which I think the latter would help create an "easy to learn hard to master" type of game.