Bpan Yaa is a game for learning the Thai alphabet. There are multiple complexities of the Thai writing system that make it non-trivial to transliterate words from a Thai alphabet to a corresponding pronunciation using English letters, such as the following:

• Although letters are generally pronounced in a left-to-right order, this is not always true. Certain vowels are written before, above, or below a consonant, even though they are pronounced after that consonant.
• Vowels are sometimes omitted and must be inferred.
• Consonants are often pronounced differently if they appear at the beginning or the end of a syllable.
• Although pronunciation depends on how a word is broken into syllables, these divisions are often not immediately clear, and must be determined by applying a set of rules.

To generate a progression of words to transliterate from Thai to English, Bpan Yaa uses a partial ordering of execution traces generated by running a transliteration procedure on each word [1]. We used the Thai-language.com Enhanced Phonemic Transcription procedure, which captures all of the elements listed above. In this procedure, 1-grams range from simple operations like basic conversions from a Thai letter to a corresponding English sound, to more complex processes such as determining whether a consonant closes the current syllable as a final consonant or starts the next one as an initial consonant. Larger n-grams, such as 2-grams and 3-grams, start to capture syllables, and even larger n-grams capture full words. Bpan Yaa includes approximately 1000 of the most common words in Thai according to Thai-language.com. The progression is constructed by running the procedure on each word, identifying n-grams, and computing a partial ordering from these n-grams. 1-grams are sorted by how frequently they appear in the word list. The progression follows this algorithm:

• Pick the most common 1-gram not already introduced.
• Add the simplest word that contains this 1-gram and has no predecessors that have not been introduced.
• Continually traverse the graph. If there is a node that has all of its predecessors added to the progression, add that node.
• When there are no more words available without introducing a new 1-gram, go back to step 1.

Bpan Yaa continually follows this progression and asks the player to transliterate words. If the player transliterates the word correctly, the game moves on to the next word in the progression. When new 1-grams are introduced, there is a small tutorial message that explains how to pronounce words with this new 1-gram. If the player answers incorrectly, the game identifies the point in the trace at which the answer deviated from the expected answer and marks that 1-gram as failed. The game then uses the partial ordering to identify the simplest word in the entire progression that contains the failed 1-gram. It gives this word next and provides an explanation for the failed 1-gram. When the player has relearned this 1-gram, the game returns to where it was in the progression and moves on.

References:
[1] Erik Andersen and Sumit Gulwani and Zoran Popovic. A Trace-based Framework for Analysis and Synthesis of Educational Progressions. CHI 2013