Hey, this is a pretty nice! It's a bit old-school and dated, but for the most part delivers a solid mini-golf experience, with everything feeling quite intuitive and plain ol' simple fun.
I found it quite amusing that it tries to be so realistic: you'd think that for Cosmic Golf, since it's a video game and thus can do anything, it'd do some wacky stuff like portals and weird gravity mechanics and other sci-fi shenanigans, but it just does what a sci-fi mini-golf course would be in real-life, which is just shaping the courses like aliens and putting glowy neon paint on everything, haha!
If I were to have complaints, I would say that the game feels rather dry and incredibly plain, lacking any sort of excitement. I'm not asking for explosions or anything, but just more subtle sound effects like the rolling of the ball, slight bumps for hitting slopes, more fanfare for getting under par, stuff like that! One part that really disappointed me was when you finish a course and it just dumps you out to the main menu: c'mon, can't there be a little bit of closure, like some sort of award ceremony where you review the score and get bronze/silver/gold if you meet certain achievements?
I also found the physics simulation for the game to be a bit bare-bones and overly flat and 2D. I know it's to be expected, but I was just disappointed that some events aren't modeled properly: for example, if you're right in front of a hole and you hit full power at it, it'll just plunk into the hole no problem, when it should fly right past it, slightly bumping into the cup as it passes over, or maybe even riding the curve of it. Similarly, I'd have times where I'd be hitting a ball up a slope with power, expecting that it should get some air time, but it just says glued to the ground. Just little subtle things like that missing which made the simulation feel rather cheap: the game is still fun overall though.
Maybe I'm being a bit unfair considering it is supposed to be a blast from the past and my expectations aren't proper for that time period, but I just wanted to give my honest first impression without taking into account that type of subtle context I read afterwards as it might help for future updates!