New game demo with the new engine and a lot of new features

Now you can play the new version with a new custom game engine base on pixi.js.

The list of improvements is huge, too much to list, for example:
- Characters are animated
- Background tiles
- New items such as the bomb.
- Different level styles
- New characters (some by me such as Niko and Enri)
- New font made  pixel-by-pixel by me
- Main character is now randomly chosen.

Some characters share the same weapon because I'm working on them right now.

Difficulty is not yet calibrated, some weapons are weak, other like Enri's atom is devastating.

During gameplay just press ESC to return to the title and try a different character/theme.