There's no stylistic or design constraints, you're free to take the project in whatever direction you wish to. The only restrictions in that area are going to be the time available and your own ability, which is why we've put a lot of emphasis on planning out your project.
Last year's base project was a simple shooter with an attract/repel mechanic - final games included first-person puzzlers, stealth escapes, LAN arena shooters, combat RPGs & tower defence RTS' : https://itch.io/c/211939/search-for-a-star-2017
On the technical side, there's no hard limit on what you can do but it's recommended you play to your strengths & adapt your project accordingly. If you're fascinated by adaptive AI programming, bring that in as a technical focus to your game. Similarly, if you spend your free time working on shaders and GPU programming, take those skills & build your project around them.
If you have an area of technical specialisation, make it clear in your project.
(spoiler: there's a new showcase award for technical ability this year)