This simple example is from Wu and Parlar (2011) and its solution is found by Gambit. Here too we find that P2 has four strategies, but you need to be careful how you interpret these strategies in Gambit's output.
This Maple file [.pdf] solves both the simultaneous game and the Stackelberg game. (The Stackelberg solution is in the second half of the document.)
Here we look at the Zeus/Athena competitive game which is constant sum. (Every constant sum game can be converted to a zero-sum game. Since the payoffs are utilities, just subtract the constant sum quantity from one of the players payoffs, and you get a zero-sum game.)
Zeus and Athena will have to decide on low (L) or high (H) production capacity.
Chance decides the market size (S or L), and neither Z or A know what will happen until after they decide. Here is the Gambit solution [.jpeg].
As before, Chance decides the market size (S or L) but neither know what it is. Now, Zeus moves first and chooses either L or H. Athena observes this, but does not know what the market size is. Gambit solves this problem [.jpeg].