That was a massive task for a game jam, so well done on getting it that far. I'd need to play a real opponent to give you some proper feedback but here's some things I noticed in a single player wander around the map
1. The Core has a longer reach than the NPCs, so you can pick them off one at a time without ever alerting them or taking damage.
2. Money seems to come in really slowly so building your first few units seem to take ages.
Definitely keep working on it though and let me know when you're free for a game!