Co-Optimized: CastleStorm

CastleStorm, available for free this month as part of the Xbox Games With Gold program, combines building, physics based strategy, and hack and slash action into one spectacular game. Featuring cartoon graphics, the story tells of the ongoing war between Knights and Vikings. Both sides can construct complex fortresses that house various training room. Players use these castles to fling projectiles, summon soldiers, and cast spells to break through the enemy's defenses and steal their flag while they do the same. Additionally, players can take control of hero characters, each with their own special abilities, to dive straight into the thick of battle.

While CastleStorm is mainly a single player game, it has an exceptional multiplayer mode. Two players come together, with one dedicated to working the castle's weapons while the other plays as the hero, who goes head-to-head against the incoming march of soldiers. Players can choose to play as any faction, as both the Knights and Vikings have kingdoms to choose from, each with unique heroes and spells. They also have the option of mix between Knight and Viking fortresses and heroes.

The fortress player is charged with multitasking between launching projectiles, casting spells like healing or shields, and building troops that march steadily forward. Meanwhile, heroes cut loose with swords, hammers, shields, bows and special abilities against enemy soldiers and heroes. But the fortress player has to be careful, because the game does have friendly fire enabled, and it's very easy to accidentally shoot your own teammate in the back with a ballista, especially when they're tied up in a sea of battle.

CastleStorm's second cooperative mode puts both players in the role of heroes. Together, they stand in an arena and defend against waves of enemies that march in from both the left and right. The goal is to keep the enemies from walking off with the flag that sits at the center of the arena.

All game modes, including cooperative, campaign, and versus, earn gold that can be used to purchase and upgrade training rooms, equipment, spells or to strengthen the hero with better damage and health. Each player earns their own share of gold, applicable to their individual games when they go offline.

As fun as CastleStorm's cooperative multiplayer is, they are limited to survival modes and the levels designed for them. It's not quite as exciting as a cooperative campaign, but the money that can be made through survival could make up for that. Gold and upgrades apply to all aspects of the game, including the single player campaign. Getting in few cooperative survival rounds could be just the thing to give you an edge while making your way through the story.

Whether you prefer the hurling boulders and rocket sheep from castle's ramparts or diving into the thick of battle as a powerful hero, CastleStorm is out to please. Just be careful where you aim the ballista. Best of all, CastleStorm can be played both online and locally across a variety of platforms including PC, Xbox 360, Xbox One, PS3, PS4, and Nintendo Wii U.

There's nothing like the thrill of competitive multiplayer, but sometimes it's better to kick back and play alongside your friends and family instead of against them. With Co-Optimized, we highlight and discuss games that are best played together.