Fin #1

In one sentence:
I wish to build a b&w (and yellow) mission game, controlled by a sandbox filled with small particles.

Questions:
1. How does the sandbox control the game technically?
2. What is the mission apart from the simple command “PLEASE PUT IT BACK”?
3. Where do I start? I need to plan the game in such a way that I can manage to build it eventually (I’m a slow code writer).

It will be beautiful.