u/Basic-System7368

I am currently using transfer window planner to get me to Duna for my first few interplanetary missions but it really feels like cheating or an easy mode to me and I really want this game to be challenging. That being said, I also don’t want the game to be challenging in the sense where I literally cannot know if I succeeded or not until like ten minutes later because I have to eyeball everything and work off of guesswork. Is there a better way without mods to determine transfer windows surely with a little bit more difficulty than just having the lines drawn for me?