The premise of my puzzle game is that it's a self-influencing geometry game, much like a Rubik's Cube. More specifically, the puzzles can always be solved with a certain order of moves, and the actual game is figuring out which moves to make.
It's fairly obvious that a game's difficulty should start out relatively easy, and end with a very challenging 'test'. Kremers - in his book Level Design - cites this as a major concern for the level designer. Kremers places a lot of focus on all games as being about mastery - that is, the real fun in most games is becoming skilled at controlling a system and achieving objectives. He stresses the importance of teaching your player new aspects of playing the game in each level, and then testing their skills, be that with a boss-fight, a difficult puzzle, or a particularly dangerous level.
Generally, it seems that a level should teach one new concept at a time. A level should never demand multiple concepts and skills that the player has not yet learned; it should only demand learning a single new skill. But that's a general guideline.
(Will Wright's demonstration of progression in The Sims. Source: https://youtu.be/CdgQyq3hEPo)
In one of his lectures on game design, Will Write - creator of The Sims - pointed out that the first hurdle for a player to overcome is the game's interface. So, for example, in The Sims, the first action a player will try to perform is moving a character, or interacting with an object. Similarly, the first level in my game simply teaches the player how to move slices to their goals:
Level 1 (seen above) includes no complications, such as locked slices or multiple gem colors. It simply allows the player to try moving a gem-slice by rotating circles - the key principle of the game. After briefly showing this to my module tutor - who hasn't played many puzzle games and was unfamiliar with the interface - it became clear that I'd also need to somehow indicate the input itself (clicking) to a new player.
Moving on to more complex levels, here's Level 2:
The concern of Level 2 is to introduce the player to 'locked' slices, which prevent circular pieces from rotating. To solve this puzzle, the player needs to rotate the blocking piece. This is another example of levels serving as a test-barrier, where players cannot progress unless they understand a key concept, thus preventing them from moving on to levels they're not ready for, and falling into the anxiety' side of the flow channel.
When creating and ordering my levels, I generally give them a solid purpose; a lesson that they need to teach the player. Each level introduces two things. Sometimes, several levels can be dedicated to one concept, especially if that concept is difficult, or needs to be tried in different scenarios (locked pieces with one gem, locked pieces with two gems, locked pieces with three gems ...).
Level 3 introduced multiple gems. It also maintains locked pieces, and features a more complex lock-conundrum, resulting in the player having to focus on ordering their moves (Does this level introduce too much? There are two new concepts and one freshly understood one. However, players seem to manage the level fine. These are the questions that I hope to gather data on).
Level 4 once again introduces an order puzzle, but this time it's more central and more concise. This may actually be a better order-puzzle demonstrator than the previous level. I may want to swap Level 3 and 4 around.
Level 5 pushes order-priming into full swing. It requires one of a few very specific solutions, requiring much experimentation. The few play-testers so far have managed to solve the puzzle in around 15 minutes, after much experimentation. They start to figure out the steps they should take one at a time. It's actually become clear that a puzzle-reset button would be great.
Note that the structure of these puzzles is, roughly:
2. Difficulty-inducing mechanic and key concept (locked slices).
3. Order puzzle (intermediate).
4. Order puzzle (intermediate/easy?).
5. Order puzzle (hard).
Ignoring the possible error with how I've ordered 3 and 4; the final three puzzles represent a culmination of understanding order solutions. This is the teach-test structure. You teach the player a concept, and culminate with a test. From what I've read, it seems that this final text corresponds to the crest of an oscillating game pace:
Following the crest of the curve (The test, in this case Level 5), the game's pace drops back to a slow one, as a new skill is introduced. Schell has discussed rewarding your player's crest-test-passes with a new mechanic, or an empowerment. For example, once you've mastered the grenade pickup, you'll always have 5 grenades each level. However, I can't imagine how my puzzle game could support this technique. Instead, each new dip-and-crest would represent a new style of puzzle; more gems, more complexity, or new auxiliary mechanics (which I haven't yet added).
My next step will be to polish the game with a tutorial, and construct a survey for participants to fill out. Then I'll gather my first batch of data.