Now I have to figure out the design. Since Project Nova is really just a learning experiment, I'm planning on making things up as I go along. But I do need to pick the basics, such as a rough theme for the game, and have some idea of what kind of shmup it should be.
So far my design is one sentence long:
"Shoot everything, and avoid the stuff that's shot at you".
To throw in a few more details, I think I'll go with a vertical scroller, rather than horizontal. I'm not yet decided on a graphical theme, however. Some of those freeware shooters that OrangyTang has suggested have a cool abstract theme, but I'm not sure I should just emulate that. I'll have to pick something without a huge amount of art assets required (I'm still a bad artist), but is still something that seems cool. I'll spend an hour or two drawing some concept art in order to make up my mind.
It would help if I had my collection of ancient space shmups, but they're all in a box back in my home city of Melbourne. Tyrian was great, but there was also all those Sierra ports like Silpheed and the slightly related Thexder and Firehawk as well. I'll need to hunt around for a few more scrolling space shmups to get a good feel of what gameplay works.
As an addendum, I still haven't forgotten about my big project, Project Hamlet. However, thinking through my objectives I think it's better to aim to make great small games first, before trying something so ambitious. It's too risky to try and become a huge success as an indie with a highly ambitious game. First I'll aim to be successful. Then I'll make the ambitious game. Somewhat strangely that way round I think I've got a better chance of actually finishing Project Hamlet than if I try it now when I'm still a bit green.