Although Avatar: The Game is named after the movie, the story itself doesn't follow the plot of the film. Instead, the player takes on the role of Lance Corporal Ryder, a signal-specialist who is sent to the distant moon Pandora. Ryder is one of the selected group of people that take part in the Avatar-program, which creates hybrids of Na'vi DNA and human DNA to better interact with the inhabitants of the planet: the Na'vi. The Na'vi are friendly at first, but humans want more than just diplomatic relations, leading to a war that only one side can win.
The gameplay changes significantly depending on Ryder's choice:
Human: As a human, the player can enter buildings, drive vehicles like buggies and helicopters, and use full-body armor as well as several different kinds of firearms. In addition to Pandora itself attacking the player, the player will also grant experience points. As a human, the player can build pods that replenish ammo and health at specific locations. Na'vi: The Na'vi are more than two meters high and cannot enter buildings or use human vehicles. However, Pandora is friendly, so plants and animals won't attack, allowing the player to ride strange horses or fly around on huge dinosaur-like creatures. The player can use a machine gun, but normally relies on bows and arrows and strange swords and staves. A special attack becomes available after pulling off a five-hit combo.
Both characters share some common aspects:
They are controlled in a standard 3rd-person-shooter-fashion and have to collect DNA/cell samples. Once enough have been collected, the player gains the ability to get back into the fight after hitting zero hit-points. If not enough samples have been collected, the player re-spawns at the nearest outpost. Both parties earn experience points for completing quests and killing enemies. When enough points are collected, the character levels up and gets access to new weapons and spells. Pandora is divided into several sectors, each featuring challenges like lifting 100% of the fog of war or collecting a certain amount of cell samples. Fulfilling these objectives grants additional experience points. A world-domination-mini-game is available at each transporter, which is turn-based and has the player starting out with one sector and the goal of conquering all others.
The game offers five team-based multiplayer-modes: King of the Hill, Capture the Flag, Team Deathmatch, Capture and Hold, and Final Fight. Money for building bases and ordering troops is earned by playing through the normal campaign, while defense buildings can be built to defend conquered sectors.