I’m 1h40 ahead of schedule, incredible! 
Interaction between the particles and the level end block was easier than expected…
The game is also shaping up a bit, I’m starting to have a lot of ideas on extra elements for the game, although I’m still not sure on how to get them all together in a fun, level-based design.
Now, complete with moving blocks:
Next up, one of the new elements: colored walls that only let pass certain colors… of course, for that to make sense, I need to have control on the type of color I’m attracting with the mouse. I have two choices: I can base it on keypresses (which kind of defeat a bit my idea of minimalist gameplay, but might lead to a game that’s more fun), or there might be elements that either change the color of the cursor (changing what it attracts) or changes the color of the particles for a certain time (or forever, not sure).
These are the small decisions that I usually have a lot of fun with when I have more time, but when I have so little time to develop a game, I’d like to have a magic ball that gives me the answer right away!