Unfortunately, Megatrix does not run well in either Steem or WinSTon. In WinSTon the controls don't work at all, in Steem that's no problem, but starting with the second piece, the speed increases so much that the game is hardly playable. Therefore, I can't say too much about this shareware game that has become quite rare.
The shareware version only offeres normal mode, where your level increases with every 15 rows you clear. The registered version also featured a mono-dual mode, where your goal is to clear as many rows as possible within the alotted time, and a master mode, where you have to clear a certain number of rows to gain access to a special level (?). I doubt that you can still upgrade, you will probably be stuck with the shareware version, which does allow for two players BTW.
