It is a very very great concept and a solid base. Actually with some improvements and more feature this would be a game that I would play as a full realease. It felt really greate when I was almost out of time but I could still manage to get back to base, so I can by some upgrades. However I have some suggestions:
- I think the movement speed should be increased becuase currently it feels really really slow. I know that would require to make the level larger as well, or the amount of time you get smaller. this is a balancing issue to be honest.
- I would also add upgrades to not increase the time, but the movement speed in percentage. That is basicly almost the same thing but you can feel the benefit directly during the level.
- I think I would rather add more gems to the level (or valuables) and not respawn them. I know the current theme was looping, but I think in a full release you don't need to stick to the theme anymore.
- also the doors should remain open and make the keys much more expensive.
I really like this game loop (hehe), that you always need to go back to base, but you always need to go farther and farther and so you need to buy upgrades to get farther for more resource etc...
Good game, keep up the good work!