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modern
Hex Blitz Rules
Hexblitz is a set of free wargames rules for modern-ish wargames on a hex grid.
Army Dudes Plastic Army Men Rules
Army Dudes is a set of free wargames rules for playing games with the classic green army men.
Snapshot Modern Submarine Rules
Snapshot is a set of free wargames rules for playing modern submarine games using 1/700 ships.
The Portable Wargame: Modern Rules
The Portable Wargame is a sort of mini-movement in the community: a series of user created rules for games based on checkers boards. They all look interesting and fun. Here are the rules for the modern version.