Play-testing is an important part of game design, not because it allows you to make sure the game is bug-free-- though all games should be bug-free, I'm looking squarely at you, Elder Scrolls IV, rassum-frassum no reversing-vampirism on the PS3 Game of the Year Edition-- but because it makes sure that the game just plain works: that puzzles can be solved, that goals are clearly stated, that the HUD is easy to understand, and that all the various systems and rules can be grasped in the blink of an eye. In some of my making-of videos for Side Saddle 2, I explained the vital role play-testing played in making sure the game was playable.Play-testing for Ultrageist, however, is a trifle bit trickier. Part of the whole point of the game is that very little of how the game works is explained; it's up to the player to suss out how the various elements of the HUD work together, to stumble upon "flaws" in the system that can be exploited for maximum benefit. It's possible to basically skip over the second and third levels straight to their boss encounters, and in all likelihood it'll be necessary for most players to do just that in order to get to the final boss.
It's the very opposite of intuitive and accessible, on purpose, though not, I must add, in that annoying I Wanna Be The Guy way. This game isn't about frustrating the player, but about the player overcoming frustration: the game plays fair; the rules are consistent and make sense, it just takes a little more time to figure out what those rules are and a little bit of strategy to get 'em to bend in the direction you want.
If the whole point of play-testing is to see if most players can grasp A and B, then a game in which the player has to slowly come to realize A and B is a hard game to play-test. Is the player confused because I did it wrong, or because I did it right? When they get the first of their big "A-ha!" moments, is it because it was well-designed or is it because it was badly designed-- for even in a badly designed game a player will eventually be able to put the pieces together if they play it long enough.
It's a tricky question, and my first round of play-testing didn't get me any closer to an answer. Though it did influence my decision to make the second level more of an overt puzzle level; the optional "trick" that lets you breeze past the first level more quickly is no longer optional in the second level but rather necessary to your progress. The puzzle format allows the game to hint at this particular system more overtly. My hope is that a player who slogged and fought his way through the first level will get stuck on the second level, figure it out, and then breeze through the first the next time around now that they're armed with additional intel. I'm starting to figure this out, I'm getting better at this: that's the feeling I want the player to have as they unlock the mysteries, such as they are, of Ultrageist.