Well, I don’t have time to make YouTube videos right now. However there already are a lot of good tutorials out there.
First of all – all the tools and assets used to create this game are completely free.
For the graphics I used KolourPaint, which is a bit like the old msPaint from Windows XP (but for Linux and with support for alpha channels). But I would not recommend this tool anymore since in newer versions there are a lot of bugs – so I switched over to Aseprite (which is awesome).
Aseprite costs 15$ but you can also download it from GitHub for free and built it from source (not sure if you can use it for commercial projects that way).
If you need good tutorials on Aseprite or pixel art in general, this guy has a lot of useful videos:
countless tutorials on the web.
Retro style sounds effects can easily be made using something like sfxr (I think I used bfxr for this game which is essentially the same).
Music is always my biggest problem. But there are a lot of free assets online that can even be used commercially (when using free assets you should always be very careful about the license). One of the best places to find free game assets (not only music) is opengameart.org.
Programming was done in a language called MonkeyX2. But I also code a lot in CerberusX (which is a fork of the predecessor if Monkey2). Both are completely free* and can be used for commercial games. The communities are very small for both of them but the people there are extremely friendly and will help you if you run into any problems.
I hope that helps at least a little bit.
* please support the developers if you like these tools.