I don't understand the levels
On each language that you do you gain XP towards the next level, but I don't see what this actually does, and I don't understand how it's calculated either.
I'm level 7 in Spanish and level 8 in German; though I only leveled up in German 21 hours ago, and since then I've only learnt 2 more skills:
The weird thing is though, that I've done so much more work in German than Spanish, surely the difference would be more than just 1 level? It doesn't make sense.
Thanks for anyone who can help!
Each level up requires progressively more XP, so you could be several hundred points ahead in German, and at the bottom of the level in Spanish. If you are 500 points ahead, that is around 50 more lessons you have done in German than in Spanish. In your profile you may be able to see exactly how many points you have in each, but maybe not as it is an AB test.
To test a new feature on a website such as this, they will often divide the users into two groups ('A' and 'B'), one with the new feature and one without it. This allows them to very directly measure the impact the new feature has on user experience (for instance, they could try to measure if the XP bar actually motivates people to learn more, or if it's just clutter). It's obviously a very useful tool, but must be used carefully since users don't usually like interfaces to change too quickly, or to feel like lab rats.