@Zarok Dai
@Bryfft
(and everyone else who is interested)
Regarding the use of "Fixed Odds" reward chests in the Spring Event (and others), you might want to take a look at a judgement by the Belgian Gambling Commission which may mean you (and other online gaming companies) have to change methods.
I'm following several commissioned investigations in the EU at the moment as regards gambling within games, and one in Belgium has finally had a judgement. It was initially an investigation into EA games, and their "Loot Boxes", but the upshot is that such rewards (where real money can be spent to buy them, and the rewards range from useless to useful) is now considered to be gambling by the Belgian Gambling Commission even if the rewards are virtual and contained fully within the game. (Unlike the US and UK, who ruled that the lack of real-money rewards means it's not gambling.)
Several of the principles the Belgian ruling outline in their decision are the same as the Chests in the Spring (and other) Events, and whilst the original judgement covers EA - who are very likely going to be forced to remove the loot boxes - it will also be applied to other companies that use similar practices. (There is another, less public, investigation being made at an EU-wide level, and the signs are that they'll apply similar protections once their own investigation is concluded.)
The judgement is at
https://www.koengeens.be/news/2018/...ie-videogames-in-strijd-met-kansspelwetgeving for anyone who "spreekt Nederlands" (speaks Dutch), but the translation via Google translate is generally accurate and the BBC have an article here.
http://www.bbc.co.uk/news/technology-43906306