Thanks for playing, I'm glad you enjoyed it! ⸜(｡˃ ᵕ ˂ )⸝
What actually happens when you "drag the background" is that you are panning the camera around the scene, I hope that may become more clear as things progress. I'm currently working on a tutorial stage as well to teach new players the control of the game, since I have received feedback about players not knowing how to play.
I wonder if you have tried the scroll wheel for zooming in and out, perhaps that would help the scroll needed for delivery issue?