Looks like you've built a good engine here. I won't mention the collision detection (oops too late) but otherwise it plays very well. Cheers for providing it
Just one suggestion. If you have empty slots in your backpack can you make Maxwell pick stuff up without having to then move the selector to en empty spot or exit? It would make for a smoother experience. Ie, pressing down automatically plops the item straight into your pack and you can continue on your way without pausing to faff a little.