SPOILERS AHEAD

Frog Fractions is, despite its name, not all that much about fractions. You start up the game, you’re a frog sitting on a lily pad, and bugs are trying to eat your fruit. If you knew nothing about the game prior to playing it, you would have no idea what you were about to experience. An upgrade converts your lily pad into a turtle that can drift around in the pond.
There are many ways that this game subverts your expectations, but, in my opinion, none are more subtle and elegant than the diving mechanic. After drifting back and forth for a while on the turtle, the player eventually realizes that the turtle moves up and down as well as side to side. Moving down to the bottom of the scene lets you dive below the surface of the pool into an underwater area with an endless supply of the fruit you’ve been painstakingly collecting over several rounds.
Finding this area is key to breaking out of the presented game loop and into the humorous nonsense that makes up the rest of the game’s content. After collecting “Like a billion” fruits from the endless fruit supply, you can afford to purchase an unreasonably expensive upgrade that triggers progression to the next part of the game. Beyond that, though, finding this room updates the player’s mental model. At first glance, the player’s mental model might have seen the first stage of the game and thought of Brick Breaker or Ball Blast, games where your character can only move left to right at the bottom of the screen. Once the player realizes that they can also move up and down, their mental model changes: Oh, this isn’t like those games I’ve seen before. Next time, when I see the frog on a moving platform, I should try moving up and down to see what happens!
After the first scene, the player is now primed to expect a room full of fruit beneath the surface of the water. So, in a later level with a similar setup, the player immediately dives down in search of more fruit. However, instead of finding a small room, the player is greeted by the mouth of a deep underwater maze. The player’s mental model is updated again.

The game has subverted the player’s expectations twice now. First, the player expected to find nothing below the water. Then, they expected to find a room full of fruit. Now, after this most recent subversion, they just expected to find something interesting below the water. The game finds a way to subvert this expectation, too.
In the final scene of the game, the player finds themself in the “Presidential Swimming Pool” on the same turtle they were on before. The player moves to the bottom of the screen, expecting to find the next part of the game… but then the game just ends. I laughed out loud when this happened, because the game totally got me! I felt so predictable because the game had found a way to surprise me not once, not twice, but three times with the exact same mechanic.

How did this third subversion update my mental model? I think my mental model now says something like: You never know what you’re going to find beneath the surface of any body of water in this game. You should expect something unusual and unexpected every time you dive.
If this is, in fact, how my mental model was changed, then I don’t think Frog Fractions could have kept it up for a fourth subversion. Now that I knew to expect the unexpected, any additional wild turns would be somewhat expected, and their effect on me would be reduced. The fact that the game stops at three was either intentional or a very happy accident.
Although I have spoiled quite a bit of the game in this post, there are plenty of other funny moments that I did not share. Go check out this game if you get the chance!