It is completely understandable to want to make some money off a project such as this, which has obviously taken a lot of time and effort. But limit it to the 'credits', so people can pay a little extra to get more models and for example the skeleton sets. But if players can't access the 'regular' models without either paying or coming back every so often to do some quiz, that discourages them from continuing. which is a shame, because this is actually a great game.
I love the way jumping in a starting elevator kills you, and falling head-first in a 15 metres deep pit doesn't... I suppose this took place in Soviet Russia :)
We all gotta eat. Ohnem like their Pixie steaks. :P