In the Gameboy Advance single player mode, there is a choice between playing campaign mode or lone wolf mode. Once a campaign level is finished, you can play it through on lone wolf. The difference is that you get one person and unlimited ammo.
In every level, you can only take four people. You can browse through the people using up and down and choose different looking armor with left and right. There are also four classes of people to choose from: Assault, Demolition, Recon, and Sniper. Assault people have good health and accuracy and use a machine gun and pistol. Demolition specialists carry a shotgun, pistol, and grenades. They have heavier armor and are slower, but can disarm bombs faster. Recon people can detect enemies in nearby automatically with their heartbeat sensors. They also carry an SMG that fires three shots per burst and a pistol. Their armor is the lightest but they move the fastest. Snipers can use their snipers to pick targets far away, but only within the sight range of the direction they are facing. When sniping, all teammates duck and let the sniper pick targets off. Most levels have hostages that need rescuing or bombs that need to be defused or both.
There are many controls to the game with different button combinations:
B - Use current weapon.
A - Reload weapon (must stay still).
L - Strafe (while held).
Start - Pause the game and check objectives.
Select - Check the map.
L+B - Perform actions (Open doors, defuse bombs, rescue hostages).
L+A - Crouch.
R+B - Aim mode (with crosshairs).
R+A - Change weapons.
L+L - Toggle between making your whole team wait or follow you.
R+R - Toggle between making one member of your team wait or follow you.
L+R+B - Switch characters