Teaching games have somewhat bad reputation. Typically, an enthusiastic teacher chirps "Children spend hours and hours playing WOW. We should make games which harness this to advance learning! Kids learn best when they are motivated and have fun!"
The result is something like Memory Cards or Hangman, which are not really learning games nor learning games, and the teachers are suprised to see that kids continue with WOW. To see why those are not learning games, imagine you have to learn 50 words for a test in 2 days. You have them prepared both as a word list and as a Hangman game. Would you use Hangman to memorize them? Hell no, it would take way too much time without any benefit on learning. To see why they are not really learning games, we need to ponder the very definition of "game".
What does it mean for a software to be a game?
Patterns in Game Design by Staffan Björk and Juusi Holpainen lists 200 patterns, which are commonly used in games. The patterns deal with the subjective experience of playing rather than structuring of game code. Patterns have names like Game World, Levels, Boss Monster, Score, Lives, Resource Investments, Combat, Ability Losses, Storytelling, Alliances, etc.
Hangman and Memory Cards implement just 3 of these patterns. They have Score, namely, how many guesses you have to do before all cards are paired or the whole word is visible. Hiding the words is an example of Asymmetric Information. The games also have a Goal.
Spaced repetition systems as games
Reports where people bang thousands of cards with spaced repetition systems are quite common. In some people, flashcard programs create gamelike ability to maintain attention. This is exactly the feature of games which teachers envy, so let's use our new yardstick to measure how gamelike spaced repetition systems are.
Firstly, they implement Score (how many cards you have mastered) and Asymmetric Information (it shows the card only after the player has tried to guess). They implement goal two times. There is the Goal of remembering a single flascard, and also the Committed Goal of flashing certain number of flashcards each day or week. The player set that goal themselves. This makes flashcard programs at least as good as Memory Cards or Hangman.
Chapter 12 in Patterns in Game Design deals with balancing. Spaced repetition systems implement Right Level of Difficulty and Smooth Learning Curve, since spaced repetition algorithms are all about showing difficult cards more often than easy ones and taking controlled doses of new difficulty.
Right Level of Difficulty
That the level of difficulty experienced by player is one intended by game design.
For the challenges in games to be interesting to players, they need to have the Right Level of Difficulty. If the challenges are too easy, players may be bored while if they are too difficult, players may give up playing game.
Example: Adventures that (sic) can be bought for many types of tabletop roleplaying games are categorized after which levels the players' characters should have. Although a Game Master may use any adventure for any group of characters, the Right Level of Difficulty will most probably only occur if the players have the right levels.
Using the Pattern: Although the difficulty of a game is individual to each player, games can be designed so that players can progress according to their own learning curve. Setting the Right Level of Difficulty in games can either be done by making challenges easier, by making challenges more difficult, or by controlling which challenges players have to meet.
Challenges can be made easier, either by providing information about how to solve the challenge or by making the actions of overcoming the challenge easier to perform, for example, by the presence of Achilles' Heels. Information can be given by Clues, Traces, Extra-Game Information, or by letting players discover it themselves through Experimenting. Making challenges easier usually requires some form of Tradeoff for players and can be done through Selectable Sets of Goals or Supporting Goals. Having to choose one goal from Selectable Set of Goals where the different goals have Varied Gameplay allows the player to choose the goal with the perceived Right Level of Difficulty but makes the other goals impossible to complete. The Right Level of Difficulty in a game can also be created by Varied Gameplay to require the players to use different competences. Supporting Goals, for example, trying to find Easter Eggs, do not have to make other goals impossible but take extra time to perform and may deplete Resources for the player.
Making challenges more difficult can be done by introducing opposition or by making the required player actions more difficult to perform. Opposition can take the form of Enemies or Preventing Goals of Agents or other players in Multiplayer Games.
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Consequences: Providing the Right Level of Difficulty in games allows players to feel Tension as there is a risk that they may fail, while giving the Empowerment since they have a Perceived Chance to Succeed and Illusion of Influence. If the Right Level of Difficulty is continuously provided for players, it gives them a Smooth Learning Curve and increases the likelihood that players progress to having Game Mastery. If this Right Level of Difficulty is due to Competition, the learning is enforced by a Red Queen Dilemma.
Moreover, people who use good flashcard programs notice the difference in their reading skill. This introduces Game Mastery. In learning games, Game Mastery is all about scalability. Players notice a boost in language skill if learning is quick and there is enough content to make a difference.
Now we have concluded that flashcards programs win Hangman and Memory Cards 7 - 3 in gamelikeness. It is debatable if Hangman and Memory Cards are games at all when they lose so easily to programs, which are nothing like games.
Making flashcards more immersive
Patterns in Game Design is not just a yardstick for measuring gamelikeness but also a cookbook for increasing gamelikeness. Sentence decks could be made more gamelike by making sentences form a terse story full of sex, drugs, violence and cliffhangers. That would add Storytelling and Narrative Structure. Cliffhangers would be Hovering Closures (events which are about to occur and can be clearly observed by players.) Desire to see progress in plot would add Anticipation (The feeling of being able to predict future game events in the games to which one has emotional attachment) and Surprises.
Slime Forest Adventure
Since spaced repetition systems are already gamelike, why not integrate one into a game? Slime Forest Adventure (SFA) does this by using an SRS as a combat system.
In the combat, you hit slime enemies by typing the correct hiragana, katakana or kanji. SRS ensures that combat is always suitably difficult. When you learn to consistently remember a group of characters, you can move to new areas as your skill is sufficient to fend off the slimes. This way, plot advances.
I was going to write that Slime Forest Adventure fails to address the fundamental problem of flashcards, making it a factlet memorization game rather than language learning game. However, the athor has added word recognition tasks for hiragana and katakana, offering very limited contextual integration. SFA could and should offer much more context to becomde a real language game.
Anyway, SRS integration makes it best-of-the-breed learning game, since competitors don't even try. SRS combat is a novel innovation, which unfortunately has not been copied elsewhere. Slime Forest Adventure is copyrighted from 2003, so this isn't even new.
Current hegemonic paradigm in teaching games is utterly flawed and provides neither immersion nor learning. This post introduced two ways to attack the problem: (1) to use SRS as a combat system as in Slime Forest Adventure, or (2) to make flashcard programs more gamelike by adding elements from Patterns in Game Design. Properly done, these approaches achieve both immersion and better learning. These approaches are old but remain unexplored.