100 to show solutions of other learners for a project's stage without solving it. (This is available only in a limited number of projects, and never for the last stage).
25 to save your daily progress with a 1-day streak freeze.
You can also exchange gems:
1 to place a bounty on your comment, and the best answer will receive it. 1 to award a gem to any comment you like using the "gem" emoji.
Right now there is no option to buy gems, but we might add this feature in the future.