Bonus coins can be used to get a premium account https...

Bonus coins can be used to get a premium account https://en.grandgames.net/premium as well as some boosters .
In addition, they can be exchanged for several thousand regular coins.

Currently, you can get:

1. For adding Japanese crosswords to the catalog. In 12-15 days after adding the YAK, its rating is checked, on which the number of added coins will depend:
3.8 and above - 1 coin
4.2 and up - 2 coins
https://en.grandgames.net /nonograms /new

2. For adding Spot the Difference puzzles (1 coin) with a rating of at least 4.0 . The check is carried out when you type exactly 30 marks.