Because blokus in its various forms is (1) deterministic (no random or hidden element in play) and (2) weighted towards one player (the one who moves first), there have been various efforts at devising variants that would compensate for those characteristics.
There are many possible trivial changes–e.g. moving the starting locations of pieces–which don’t seem to me very interesting. But there are 3 major ones that are of serious interest.
This was devised, I’m told, by Bernard Tavitian himself (creator of blokus). Though in principle it could be used for any Blokus variant, I’ve rarely encountered it with Duo; it has however become the standard means of play among top-level C2 players. (I can’t vouch for Trigon as I never play or watch it.)
The idea is that there’s a preliminary round before actual play begins. Player A names two starting pieces for blue and red to play. Player B then has the option of either (1) taking blue & red & being required to use those pieces on his first move with each colour; or (2) ceding first-move advantage to Player A; Player A then is required to play the pieces he/she named.
The beauty of this variant is that it gets away from predictable openings without totally changing game play. Player A will not name a standard, powerful opening (e.g. L5/N), because then this is just handing that advantageous opening to Player B. But neither will Player A name something absurdly weak (e.g. I1/O4) as then Player B will surely decline it & Player A will be stuck playing that absurdly weak opening as blue/red. So Player A will name something that’s neither overpoweringly good nor obviously wrong.
Though this solution could be used for Duo, I think it tends to be disfavoured because the game has so little margin for error or less-than-optimal play. Nonetheless, I think it would be worth experimenting with. So if anyone wants to give it a whirl with me….. I think this would probably require some further refinement, since whereas with C2 placement of the first pieces has little scope for choice (since two sides of each starting corner are blocked off), with Duo’s mid-board starting points you could play an optimal piece in less-than-optimal conditions. (For instance, Player A would be foolish to call out “X”. But he could certainly call out “X with centre on the dot” & that would be a good call: neither a terrible opening nor a totally strong one.)
Not sure who thought of this one, or who thought up the name. It’s the most obvious but least interesting variant: whoever gets fewest rather than most points wins. One big disadvantage of this one is that it can only be played in Training, since the software won’t recognize this variant & will thus dock points from the “winner” rather than the “loser” of a game of Glofus. — Experience shows that orange can usually win this one without much trouble, as you’d expect; possibly if people worked harder on strategy then it would be easier to devise ways to win as violet, but I don’t think this variant is interesting enough that anyone will put the necessary time in to do this. It’s more of a stunt or a pass-the-time amusement.
This one is devised by a player called pentti79. I’ve encountered it with Duo, but there’s no reason it couldn’t be used in C2 or Trigon too. The rules are simple: you are only allowed to play a piece named by your opponent, but you can play it wherever you like. In addition (to avoid running down your opponent’s clock unfairly), you must place the piece AFTER you name the piece your opponent must play on the next turn. (Thus this game is not amenable to very short clock times–like 5 minutes–as you need to allow for time to type piece-names; this is especially crucial in endgames as there is only one clock running then, & the endgame is of course dictated by the player who runs out of pieces first.)
This sounds awkward and silly, but it’s actually a fascinating twist to the game and deserves to become a more widespread variant. The amount of pretzel-logic required to see ahead even two moves is quite formidable, and while I imagine that eventually the opening and midgame strategy will be mapped out in more detail for the moment even basic strategy is not well-known. From the few games of it I played the other night with iwk, it appears that (1) the temptation (bad or good, I don’t know) is to call out the small pieces first, of course; (2) calling out very awkward pieces like I5, O4 or V5 at the right time is the real building-block of strategy.