7 hours to get all Steam achievements, mostly without hints.
That works out to 3 minutes per puzzle, and that's not including the victory gift animation.
This is a collection of easy to medium (at best) puzzles of 14 types. The most interesting one is the code puzzle, but there are only 35 of those in challenge mode. Most of the puzzle types suffer from the small size; they seem designed to be displayed on much smaller devices than computer monitor.
Localization: You have a choice of British and American English, plus 4 other languages. The german localization is patchy, with "Wortkette" converting ÄÖÜ to AOU, and occasional spelling errors (most noteable "Paneten" having the planet "Merker"). Also, the German keyboard layout doesn't work (Y <-> Z).
Although it's on sale for -.99, I give it a thumbs down since I know a few independent puzzle games that give more bang for your buck, e.g. the games by Kris Pixton or Everett Kaser (not on Steam). You can play those games for years, and their difficulty starts
at 3-5 minutes per puzzle instead of ending there.