As a class based, co-op game the playable characters and their abilities form the basis for the gameplay. So it was essential to get these designed first. The Classes and their abilities are what determine the level design.
The Disarmer is equipped
with a shovel and a bomb diffusing kit and is responsible for disarming the
mine; everyone in the team is there to provide support for the Disarmer so the
mines can be defused.
Before the mines can be
disarmed they need to be located as they can be buried anywhere underground,
this is where the Locator class come, they carry the Bomb detector which beeps
when it detects the mine. The Disarmer and the locator work together side by
side.
The Distractor usually stays away from these two
and tries to lure the guards towards him so the first 2 can locate and diffuse
the mines. They can distract the enemies by whistling or throwing rocks;
whistling will bring the enemy towards the player, while throwing rocks makes
the enemy move towards where it was thrown. Thus the Distractor can keep the
enemy AI away from the locator and disarmer by strategically using a combination of these 2 abilities.
Lastly we have the Support class, they can provide cover by blanketing the area with smoke, which can either be used to block the line of sight of the enemy AI so the players can sneak past them through the smoke or they can hide in the smoke while defusing the bomb. Support class can also heal wounded players by dropping med-kits upon request.
The primary design focus here is to have classes that are fun to play on their own, but team work is essential to win the game. No one can win the game by themselves . and is encouraged to seek assistance from and provide aid to others to accomplish the objective.
To further reinforce this point, Czech hedgehogs are introduced in the game. These were widely used during WW2, to stop tanks dead in its tracks. These are placed in checkpoints between the zones to prevent our armies infantry and tanks from pushing in.
So in order to win, the hedgehogs have to be displaced, which requires all 4 players to interact with the colossal thing and move it out of the way. This in turn forces players to cooperate to complete the objectives.

