Better debugging

[yancouto]

We'll definitely need some step by step interpreting, and showing this to the player.

[yancouto]

We show step by step of the expression being evaluated. It's pretty ugly though, just a wall of text, which makes it super confusing.

[yancouto]

Text is printed better, but it's still a wall of text.

[yancouto]

It's basically impossible on the more advanced levels. But I don't think doing step by step resolution, even if it's a good UI, will be enough.

[yancouto]

Debugging had fully_resolve: true, which made it really hard to debug.

Now it's easier, though still very hard in any non-small level.

[yancouto]

Playground screen implemented, which helps.

Step by step would still be cool.