Thanks for playing and appreciate the feedback! I'm not sure if or when I might do more with this, but I very much agree with your suggestions.
The combustion engines especially are arguably even worse than useless. If you waste too much fuel with them, you can stunt your progress. That said, I'm not sure I'd completely remove them, especially if I took a narrative route with future development. There's maybe something interesting there about technological obsolescence.
Yes, I pressed that reset button after I found out I wasted too much fuel with the combustion engine.
If you decide to keep those obsolete techs in the tech tree, I think you can add the ability to hide certain techs. This prevents too many obsolete techs from cluttering.
If the combustion engine is kept, I think it needs a redesign: Since the fuel efficiency is all what matters, you can increase its base efficiency a lot, but make it not scale proportionally to number of engines. This makes it useful at start, and fusion is still a big improvement.
Alternatively, the real time research speed could be based on proper velocity, so increasing velocity early is still helpful, allowing an early engine to exist.
Another note: When fusion is unlocked, it's relatively easy to research the efficiency curve to high levels. This basically makes that efficiency irrelevant because it's near 100% all the time. This is even more true for antimatter engines. So I think the whole efficiency mechanism should be removed for the fusion and antimatter, and leave it exclusively to combustion engines.
