I really liked the take on Connect 4 with the added enemy modifiers like The Blocker, Gravedigger, Architect, and Mirror. Each one changes the way you approach the board in a meaningful way, which makes the classic formula feel much more strategic and fresh.
The chip-based upgrades were also a nice addition and gave some extra depth to decision making. Overall, it was a simple base idea made much more interesting with creative mechanics. Good job!