4.2.3 Level 5
Level 5 (Figure 12(a)) requires the player to rotate a laser counterclockwise to reach the target, but is only given three pieces that all rotate the laser clockwise.
Therefore, the player must place all three of these pieces so that the laser bends all the way around.
From the visualization (Figure 12(c)) we can see that roughly 20% of the players go into the cluster visible in the upper left.
This cluster corresponds to game states where the player incorrectly tries to use a clockwise-rotating piece as a counter-clockwise-rotating piece, even though the pieces cannot function in this way (Figure 13).
Our visualization quickly draws attention to this area of confusion. In fact, the visualization shows that players do not make the same mistake with the other incorrect piece.
One possibility is that the laser does not show direction clearly enough, so that players cannot tell if it is traveling from bottom to top or top to bottom: in that case, placing a piece that accepts the laser from above would be logical.
The other possibility is that players care about the piece's exit direction and not its entrance direction.
The target is to the left, so a player's instinct may be to place the piece that points left.
In either case, using Play tracer reveals a cluster of similar problem states that the game designer can investigate further through traditional play testing.