Thanks! The game was originally developed for desktop only and the web version has it's quirks with espace key because of that. I will try to figure out something to make it better.
There is a setting to start the next level that shows up after you finish it ;)
The golden AK and other quests can be found in the quests tab. It's accessible in pause menu or main menu. The portal gun is an easter egg :)
Thanks for playing and please consider rating the game, it really helps. Cheers!