Small Winter-Update

It has been already months (I think) since I made a quick update to my game. So I decided to work a bit on it now and here are the results:

- some changes for Endless Mode Map 2 i.e. correct shadows from the buildings

- details like ejected shells from the guns laying on the ground

- medkit icon has been changed

- some winter-like vibes in the menu

- few little fixes

- more different sound effects

I know it is not that much but until the next level is finished, it will take some time. The update should be available in the browser as well for download right now.