Hi. Thanks for trying it!
Regarding the trajcetories, the sourcecode is written in C# but if you want to take a look at it you can find it here https://github.com/Heartstop/SpaceExplorer/blob/master/Scripts/Actor/Trajectory.cs
TLDR is that we implemented gravity force and used the same code to predict were the ship was going to be in the future :)
One of the things that we failed to do was telegraph to the player that after their first and second upgrade, they can zoom out more. It sounds from your difficulties that maybe you tried to aim for the Icons instead of the planets? Correct me if im wrong :)
Thanks for letting us know that the game didnt load for you... I am on Chromium 108 and it works for me but maybe its safer to upload a executable to be sure that the game can be played.
Thank again!