"The Battle for Wesnoth is a turn-based strategy game played on a hex map, with single-player campaigns as well as multi-player matches. A central philosophy in the design of the game is the KISS principle (keep it simple, stupid); for a new idea to be accepted, it should not complicate gameplay.
Each unit has its own strengths and weaknesses. A unit's defense is based solely on the type of terrain it stands on, making terrain and placement of units very important. Different types of attacks (melee and ranged), weapon types (pierce, blade, impact, arcane, cold, and fire), and a day-night cycle that alternately favors lawful and chaotic units, add to the strategy. Throughout the campaigns, units can advance to higher level counterparts and become more powerful. Part of the fun is developing a personalized army of advanced units as a campaign progresses."
If you like games like Advanced Wars, Fire Emblem, Vanguard Bandits or Heroes of Might and Magic you will enjoy this free game.
I play it windowed and other stuff while I am fighting with someone online, hinders no progress in my online duties or personal shit.