By chance, I have found an exceptional collection: "Sonic" (2012-...), of Aleksey Krupenko. So far there are 67 small storage levels, in the style of Thinking Rabbit, but of a high quality, carefully studied, and very well built (are rare the levels at which there are double interior walls, which indicates a good construction). Each puzzle is a little gem. In general, they recall the style of Jean-Pierre Kent (1998).
You can download this collection here:
• Sonic (67 levels)
If you like storage levels, this is your collection. There are some levels quite difficult, even for the experienced player (for example, 19, 20, 39, 49 ... ) and some maddening (for example, 36). Other levels are fantastic, incredibly good, my favorite is the level 58. But all levels are interesting and beautiful. Enjoy!
Source of the levels
The first 26 levels are the "Sonic" collection included in the program Sokoban, by Mack (Maxim A. Novikov; Ostrov, Russia). Website: http://soko-ban.narod.ru/f_main.htm.
The other levels (#27-67) come from the website Sokoban online game, posted by its author (see "Submited Collections"). The "Sonic" collection is here: http://www.game-sokoban.com/index.php?mode=ucollection&cid=76
The "Sonic" collection does not seem closed, because periodically Aleksey Krupenko adds new levels to the series.
I have written twice to author of puzzles (in English and Russian), but has not answered me. I hope not to bother if I share this excellent set in this blog. Anyway, if Aleksey Krupenko reads this post, I really would like him to contact me.
Obviously, the order of the levels within the collection is provisional, until it is validated by its author.
If you like these levels, I hope your comments.
Přemysl Zíka sent me this comment:
And the collection Sonic from Aleksey Krupenko... I could not resist. I put into it - and all (rooms 28-67) for yesterday and today are resolved... "Ahhh, I grunt bliss" (I do not know if Google translate well; in Bohemia sometimes say: "chrochtám blahem"). The best collection of the last period!
I agree with you: The best level is # 58. Excellent are also: 10, 19!, 20, 23, 32, 33!, 40!, 43, 56, 60, 66 etc... There is no "weaker" room.