The look and feel is pretty nice, with simple but good looking visuals and a nice ambient music. Like most I had a hard time understanding the mechanics initially, so didn't enjoy my first run so much - then I read comments and saw explanations for the heat transfer mechanics, and it became more strategic and fun (and easier to survive a bit longer :)). So an instructions screen would definitely go a long way to make things clearer.
BTW, answering "Yes" to "Is this your first Godot project" is a bit cheating when you're written a whole tutorial series about Godot :P