Unify terminology: tasks vs. problems vs. games vs. challenges

[effa]

Which is best?

[xpelanek]

I vote for "tasks" or "problems" (no strong preference among them at the moment).

("game" ~ Robotanik as whole; not an instance; "challenge" ("mise" in czech?) ~ specific selected task or series of tasks, which is especially challenging / leads to a "badge" ....)