Just bought it and played a round by myself (wife promised to play a game with me later). Seems simple, but fun. I can immediately see it would be even more fun

Just bought it and played a round by myself (wife promised to play a game with me later). Seems simple, but fun. I can immediately see it would be even more fun with 3 or 4 players rather than 2. I haven't deeply explored the game yet, but having an AI and the possibility of unlocking additional weapons/upgrades would be exciting. Also, I'd love to have online multiplayer or team play (me and a friend could get online and play against another two-player team).