A variation or iteration of the previous work, this piece maintains a similar minimalist character. It is distinguished by its subtle rhythmic variations throughout.
The challenge lies in making the subtle changes in phrasing sound natural.
Comparable difficulty and character — good candidates for what to learn next.
At That Time is rated Henle level 3 of 9 — late beginner repertoire, roughly ABRSM grades 4–5. In the RCM system it corresponds to about level 3.
You should be comfortable at Henle level 3 — meaning you can already play level 2–3 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of At That Time lasts about 2 minutes.
At That Time is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.
Pieces at a comparable difficulty and character include At That Time by Rufus Lin, Ballade by Rufus Lin, Bogurodzica by Adalbert of Prague — see the full similar-pieces list on this page.