So essentially the changes I made are:

1. Create a WinForms app instead of Console (obviously)
2. Move my game loop code from a for loop to a timer Tick
3. Move UpdatePlayfield() into the form Paint()
4. Change WriteAt (which wrote on the console) to DrawCell (to draw on the form)

That's pretty much it! Apart from some minor stuff which I'll go into next post.

Some of the code can still be removed, e.g. there's no need to 'erase' the last snake tail piece as in the console version, and we could use different keyboard technique, but it works

BTW I'm not saying this is a great design, it's quick and dirty to be honest, which was the original intention (to get it done fast, but not throwing good design right out the window..)