My (fledgling) idea:

OK, so I did promise to do my game using HTML5 and I’m not going to reneg on that one. For Tiny World I’m going to do a variation on tower defence, where you are a colony of ants. For my first prototype, which should hopefully take about 12 hours to finish, I need the following features:

You can place an ant hole within range of your main nest mound
You can draw a line from the hole to a nearby resource
You can station soldiers on a line, and they will patrol up and down it
Worker ants move up the line to the resource, harvest it, and then move back down.
Waves of creatures come along periodically, and you must watch in horror as your little ants fight for their lives.
Between waves, you can upgrade each hole, adding new workers, new soldiers, or changing the path.

The graphics are going to start off simple, of course, I’ll draw a very basic ant hole and 2 types of ant, the enemies will just be blocks until I can make them more convincing.

I imagine many other people will be doing something ant related, since ants do live in their own “tiny world” so hopefully mine will be more engaging than all the others.