To kamyon95Few years of development and some coding experience, that's how it's done.
There are a lot of coding tutorials for HL on the net, they can help you much.
To LoulimiThank you!
Yup, I am
Yeah, I got Greenlight page filled, but I'm waiting for a good day to make a nice trailer video for bdef. The mod will be submitted as a concept, it will get reviews and thumbs up, but no way for distribution on Steam at this time.
To ninja defuseYes, sure, there is a MapSDK on ModDB page including tomb map source and FGD file. You can see how the system works by opening map source from MapSDK. Mapping tutorial needs time to be written. I have a snippet of future mapping tutorial, but it covers just a little bit of bdef mapping for now. If there will be more people interested in bdef mapping it can make mapping tutorial post faster.