Yeah!  Late start!  Themes: dirt, drill, demolish.

You’re in a rocketship trying to drill its way out from the planet’s core.  Because your species crash-landed so hard 15,000 years ago that they ended up at the middle of their planet instead of on its surface, and only now have developed the crucial rocketship-drilling technology required.

Here’s a rough sketch, probably completely unlike how it will actually turn out:

To be done:  nice vertical scrolling in HTML5, hex tile randomly-generated world, a rocketship that crashes through the ground, and a surface to get to.  The art will be weak.