Todo
----
+- tux sometimes makes short jumps in the endsequence, mostly when
+ going through the goal with a small jump, might be old_up related
- fadein/out for intro/extro would be nice
- when you interrupted the intro (by going to credits for example) and go back
to it, tux doesn't jump anymore
- when jupming against the 2nd multiple coin block in a level only 1 coin will
come out.
-- In the "Oh No More Snowballs" map, there's a ?-Growup-Block at the beginning
- with only 1 tile space above it
- when jumping into the exit with a star, the endgame music will change back to
levelmusic after a short time
- the can_jump flag should be based on a time instead of the 2 tiles check.