There's not much more to Pathology than what we've already described. Each turn, you choose one of three square tiles to place on the 6x6 board. Once placed, tiles remain for the rest of the game so, at most there can be 35 moves since there are only 35 tiles (by the 36th move, all pawns would be off the board anyway). Pawns travel automatically, so you never need to agonize over whether to move them or not. Really, all you must do is pick the one tile from your hand of three that best shifts your pawn into a safe position. Sometimes you want to get as far away from other players as possible so they can't affect you, other times you want to get up in their face to try and drive them off the board.
What really defines the game is how many people are playing. Played with the full complement of players (8), the tabletop game is pure chaos. There will be seven tiles played between your own moves, and that means you have control over very, very little throughout the game. Played with two, though, these numbers mean the chaos has become a tight and controlled duel. If two experienced people who have memorized the tiles sit down to play, the chaos diminishes even further. It's not as pure as chess – there is still the luck of the tile draws – but it's a quite elegant affair.
There are two big differences between Tsuro and Pathology. The first is the look of the game. Instead of dragons and Asia, the app has, well, colors. You get to choose the background color on the tiles, but the look is plain no matter what you do. Also, the app allows a maximum of six pawns, either human- or computer-controlled, on the board. When multiple people play, everyone gets to see everyone else's tiles, something that doesn't happen in the tabletop game or even against the AI opponents.
Pathology also suffers from some non-intuitive input issues. Just getting the app to understand where your piece will start can be difficult. Sometimes it just doesn't register any number of taps – one, two, three or as many as it takes until the frustration wears off. This is because Pathology uses a lot of two-finger touches to confirm inputs. You put your token on the board where you want it and then touch with two fingers down to lock it in. Same with the tiles once you begin placing them. Use one finger to drag a tile into place, tap to spin the tile (or rotate two fingers around the tile) and then tap with two fingers at once to finish your turn. It takes a little getting used to, but it works fine once you figure it out. If you haven't played in a while, it can be frustrating to relearn these inputs.
In my game group, Tsuro often comes out when we have a lot of people ready to play but we know someone else is about to arrive. The game sets up so fast and is over so quickly that it's easy to fit in almost whenever. Pathology offers most of the same gameplay options (minus two player slots) with zero setup, so it's even faster. Is it worth $3 (or $5 for both versions)? To some people, yes. You might not spend a lot of time with the app because games are over so quickly, but you'll likely get a lot of games in, which is just what's called for sometimes.