I'd like to suggest an optional four-button grading mode when using FSRS.

Currently, Mochi keeps its binary review model even with FSRS:

• Forgot → equivalent to FSRS "Again"
• Remembered → equivalent to FSRS "Good"

I understand and appreciate the reasoning behind Mochi's simpler binary grading system. Reducing the decision overhead during reviews is one of Mochi's strengths.

However, when explicitly choosing FSRS, I would like the option to use its full four-grade scale:

Again · Hard · Good · Easy

The distinction is useful in situations where recall is not simply binary.

For example:

• Again — I could not recall the answer.
• Hard — I recalled it, but only with considerable effort or hesitation.
• Good — I recalled it normally.
• Easy — recall was immediate and effortless.

FSRS models these outcomes differently when updating card difficulty and stability. With Mochi's current binary interface, both a difficult-but-successful recall and an effortless recall have to be recorded as Remembered, so that additional information is lost.

Fuzzing does not address this distinction either, since it randomizes due dates rather than representing recall difficulty.

Suggested implementation

I would keep Mochi's current two-button interface as the default and add an optional setting such as:

«FSRS grading

○ Simple — Forgot / Remembered ○ Detailed — Again / Hard / Good / Easy»

This would preserve Mochi's simplicity for users who prefer binary grading while allowing users who deliberately choose FSRS to take advantage of its full rating scale.

Keyboard shortcuts such as "1", "2", "3", and "4" would also make the detailed mode very fast to use.

I don't think Mochi should necessarily adopt Anki's review UX as a whole — only expose the additional FSRS grades for users who want them.