[H] Make sure there are no invalid tile numbers in the level files
- Tile 6 occurs in world1/level5.stl as well as other levels
+[H] Adding objects should be done by adding them into a queue and then
+ physically added at the end of Sector::action()
+ - may cause crashes otherwise (due to iterators)
+ - see world1/level7.stl, killing the bombs
[H] Worldmap needs to allow multiple maps
+ - or just one big map with multiple worlds?
[H] Change resolution to 800x600
- Levels need to be updated to resolution
(half of the levels have been already updated)