Thanks for the comprehensive feedback, glad you liked the game.
You're not the first person to mention the unavoidable fire imp attack! To be honest, I put it there deliberately because I'm a horrible person who likes giving out nasty surprises ;-) If anyone finds their way into the secret tunnels, there's a *really* nasty (but very avoidable) surprise lurking.
Re arrow keys moving the scroll bar, that's not good and I'll try to disable that in future. The fullscreen button in Itch is problematic as dynamically resizing, once the colour mode is selected, would require major internal modifications. Probably something I'll address if I write another JS game from scratch in future.