Hey, thank you for all your feedback!
The tutorial does actually have instructions to use the left/right arrow keys. The below text box is the last box before you first select the first spawn point.
But I do absolutely see what you mean, it is a bit confusing. I guess it was just a random decision I made a long time ago and haven't been bothered to change. So I'll try it out and hopefully add it in the next update if it feels better. I hope you had fun playing and I appreciate all the feedback!