Thanks. I want to edit the player speed and jump height/distance.
you can use another program to extract the unity project out of the game files called utinyripper (download here), however it will only extract assets like textures and audio, without any code. If you want to get the full unity project files, I managed to find them here. Download them by going to Code > Download ZIP.
use Unity 5.4.5 to open the project (Get here), although there might be some problems with this.
1. Download the ripper here: https://github.com/mafaca/UtinyRipper (Click "download now").
2. Run "uTinyRipper.exe", and drag the "Rooms_Data" folder into the window.
3. Click on "Export", and select where you want to extract the project files to.
4. Download unity 5.4.5p5 here, and open the exported project files in the editor.
It seems that uTinyRipper is unable to export scripts and shaders properly, so if you try to play the game in the editor, it won't work. A better way to do this is to Download the already existing project files from the creators github, and then open them up in unity.