Hi, thank you! :) There will be more levels, the plan is to release a full paid version of the game with ~15/20 levels by the end of this year (if everything goes to plan). I have 9 levels completed so far.
You can sign up to be a playtester here. The next round of playtesting will probably be in spring when I have a few more levels finished, so if you sign up you'll have the chance to try out the new levels then.