Puzzle games break down their aesthetic experience in a lot of atomic units called levels. The game is played mostly inside those levels, but since there are many of them, how do players get to them? or more broadly, how will players and this mass of levels relate?
Level selectors are the most common answer to this question because they happen to perform several functions: they inform how much of the game you have explored, offer choice on what levels to play and complement the in-level aesthetics.
Informing ProgressMany level selectors allow you to see at a glance how much you have explored of what the game offers as well as what's left. Managing this information needs some care, as many people feel overwhelmed when looking at a giant grid of unsolved levels, and it can be perceived as "you will have to solve this giant amount of levels" instead of "you have so much to play with!". I am not sure how this phenomenom occurs, but the old stable version of Storyteller suffered a bit from this:
|This feels busy...|
Choice PowerThe primary function of level selectors is to choose a level and tell the game you are ready to play now. There's many situations in which players want to choose: they got stuck in the default level progression and need a fresh challenge, they are bored of certain type of challenges and want some variance, they are too tired to play serious challenges and want to play lighter puzzles if available, or maybe they want to replay old levels where they didn't do a good job.
There are several levels of choosing power...
No control: this means there is no level selector at all, or is limited to reporting progress status and offers no choice other than "start current level". A game must be extremely confident on its level pacing and feel its in-level gameplay is aesthetically enough on their own to do away with interactive level selectors. Probably a lot of people quit these puzzle games if they get badly stuck and are not completely engaged with the game yet.
|Naya's Quest has no level selector, levels must be solved one after the other.|
Linear Progress: players must solve the current level in order to play the next one, but they can "revisit" old levels to get a reward or just to enjoy them. There could be a bit of branching where you can pick between a couple of levels sometimes, but it's nothing complicated. This allow tight control over the level progression but allows players to escape it a bit, giving them some breathing air.
|Ironclad Tactics has a linear progression but each level can played repeatedly to achieve special goals that give you extra powerups to play the rest of the game.|
Hierarchical Grouping: Levels are grouped hierarchically and sometimes you can start playing levels from the next "sector" before you completed the previous one. Grouping levels this way is tricky because well designed levels use a mix of the game's capabilities and they are hard to classify by any criteria, but it makes the whole game feel smaller and more manageable.
Concentric Progress: instead of opening "tracks", the game progressively unlocks a bunch of levels every now and then, giving freedom to players to pick from a wide range of options. The downside is that it can be burdensome for some people to figure out what to do next, and developers have less control over what is going on in the players' heads when they pick a puzzle. I find this fascinating because the custom order in which they solve puzzles creates an aesthetic experience unique to each person.
|The Witness allows players to choose from a very wide range of puzzles to solve next, players just walk up to them.|
Complement the in-level aestheticsEverything that happens to the players with the level selector becomes part of the whole experience of the game, no matter how transparent a level selector tries to be.
Often level selectors try to be "audiovisual sugar" that gets you excited about playing another level. In many cases, the selector is the first thing players see, so it becomes their first impression of the game.
But they often feature alternative economies as well. Some games allow configurations (ie: building your deck for the next card game battle), feature upgrades, unlockables or some kind of scoring. These systems will be an inseparable part of the core gameplay of the game.
Aesthetically speaking, I observed three levels of integration...
Orthogonal: Level selectors like this are minimal and try to intrude as little as possible between the player and the levels themselves. Many flash games use this system because it's simple to implement and their players are culturally used to it anyway, so it's as close to complete transparency you can get if you still want to provide a level selector.
|Just a grid to pick levels and keep track of stars. Minimal aesthetic aspirations.|
Thematically Integrated: The level selector feels like part of the rest of the game thematically, but the interaction is qualitatively different from the aesthetics in-level. The level selector can have interactive systems that complement the in-level gameplay.
|Infectonator: you are a deadly virus killing people off, the level selector lets you choose next victims and upgrade. The interaction with it, however, is totally unrelated to the in-level gameplay.|
|X-Com: Enemy Unknown, like infectonator, the base provides a relatively thin metagame that is aesthetically different from the in-level gameplay.|
Seamless: Each puzzle is a corner in a continuous world that blurs the line between the in-level gameplay and the level selector.
|The Witness is an unprecedented (and surprising) integration of individual puzzles and the world they are in.|
I just spent several hours typing this, so I'll leave the Storyteller case for next week!