html5 connect four2 4-in-a-row strategy game1 adaptive difficulty ai1 classic vertical connect game1 clear four bubbles game1 color-matching board game1 connect four game1 connect four online1 customizable grid sizes1 educational stem game1 falling bubbles puzzle game1 family-friendly strategy game1 mobile-friendly connect 41 modern connect four clone1 multiplayer disc-dropping challenge1 oversized grid mode1 play connect four1 play vs ai computer1 quick-thinking drop challenge1 tournament-style connect four1 two-player logic puzzle1