I took turrets, gels, deadly goo, cake and a portal gun from the famous puzzle game Portal and recreated them in vanilla Minecraft. Yay! (I'm honestly sorry about the lag, there's really nothing I can do about it) Spoiler: Extra credits Thanks to BetaTheData for the Turret model. Thanks to Marijntjep for the Portal Gun model and sounds.
I'll probably repeat this sentence many times in the future. Everything is possible with custom models. I didn't make the Portal Gun model and sounds though, nor the turret model. Check the extra credits to see who made those. Everything else though, I made. Yes, the portals are also models. Yes, the gels are also models. Yes, the cake is also a model. To be honest, I thought more people were going to react to the GUI than to the Portal Gun, but I guess that's less obvious.