Frozen Synapse is the ultimate tactical game on PC and Mac.

It brings the simultaneous turn-based strategy genre bang up-to-date and lets you give detailed, accurate orders to your squad: classic gameplay with a modern interface. Plan your moves, test them out, then hit the "Prime" button: both you and your enemy's turns are executed simultaneously. Competitive-but-intuitive multiplayer and a huge single player campaign mean that Frozen Synapse will give you hours and hours of tactical delight.

Features:-

• Unique simultaneous-turn-based gameplay!
• Multiplayer: Hostage Rescue, Disputed, Secure (bidding-based mode), Extermination, Charge
• Single player: Campaign (55 missions), Skirmish Generator, Instant Skirmish
• Advanced Map Generator
• Email notifcations mean the game can effectively be "played by email"
• Community features: Friend List, rate and comment on games, Personal Feed, various ranking systems, Instant Matchmaking
• Easy match export to YouTube
• Slick, modern UI to make planning simple and intuitive
• Evocative music and audio by electronic musician nervous_testpilot
• Facebook and Twitter integration

(Official site)