What the original shows
The author describes it as close to a joke app made to test Opus 5.5 and invites people to modify it freely. The repository is public with a live demo.
Supporting documentation (opens in a new tab)Why it is interesting
A rare case where a model demo became something other people—teachers—wanted to use, with source you can inspect.
What remains unverified
The code is MIT, but the “Dopakichi” character and the “Dopa Drill” name and logo are excluded; commercial use of them needs the author’s permission. The Opus 5.5 claim rests on the author’s statement.