The game is simple-- create lines of 5 Xs (or 4 in the 4T variant) and connect them. Lines can intersect and join at the ends, but cannot overlap. You can only draw one line for each X you play, so choose wisely. The game is over when you can no longer place any more Xs. In the 5D and 4D variants, the rules are the same except lines in the same direction cannot join at their endpoints.