why 2-players at arena?

[SaggySag]

For those who think, "if I know I'm loosing, why should I waste more time?", hear my advice:
If one can't stand loosing, stop playing!

Of course I know this isn't what you mean, but that's literally what they did. They were losing, so they stopped playing!

[Sonid]

After playing 2p for awhile, I admit it is more fun than I expected. I still would be very grateful to not have to play another game on the base map for a long long time, but I guess that just makes the in person sessions with expansions and extra maps more fun.

[Cyphen]

My favorite player counts for Terraforming Mars is 3P, then 2P, then 4P, then 5P.

Both the 3P game and the 2P game have interesting balance between "engine" and "terraforming" strategies, which difficult decisions around pace-control. They also allow for more interactive card-drafting, which brings out a lot of interesting and skill-testing decisions in a game. 2P doesn't suffer from the king-making issues of 3P (if two players are strong, and a third one is much less experienced, then poor decisions by that third player is often more of a deciding factor in which of the two strong players will win than the decisions of the strong players are), which I think is why much of the competitive community prefers it. The pace of 3P games is "just right" for me though, and I appreciate the non-zero-sum nature of the "hate" cards (such as Heat Trappers and Raiders) in 3P making those cards more 3-dimensional.

As such, I'm quite happy to see Arena alternating between 2P and 3P on a season-by-season basis. I think that's the perfect spot for Terraforming Mars! The formats are both competitive, interactive, and

I find 5P almost unplayable, as there are so few gens that it's really just a race to play the most terraforming cards. The game just boils down to who got the most terraforming cards in the draft... player skill and decision-making are almost meaningless (as long as you and your opponents know what you're doing).
4P runs into similar issues with highly skilled players... but with medium-skilled players or players with little experience, it still plays alright. Generally in this game, the more players there are the less interactive the draft is, the higher-variance the game gets, and the less room there is for Engine strategies to breathe. So alternating between 2P and 3P means we keep the game at its most interactive, which is where the interesting decision-space is! I support this decision!