Level 15. Coolie Mines

Start the level in front of a bridge. To your behind left are some small medikits.

As you step onto the bridge, two doors will open from the sides with turret guns behind them. Take them out or jump to the other side where the Uzi is.

One of the turrets has the RED KEY behind it. Grab it.

Jump back on the bridge and proceed into the Coolie Mines.

Down the other end, you'll find the BLUE KEYCARD. Grab it and head back out.

Turn right and go down the other path, killing rippers along the way.

Continue down the path, past the drill, until you reach the red key door. Use the RED KEY to open it.

Hit the switch on the left. The lift will come up with the Serpent Boss. Defeat the boss.

Take the lift down. Ahead is the blue key door. Use the BLUE KEYCARD to go through.

Keep going down the path, past the drill, killing enemies.

You will come to an out-of-control drill. Break the window and go through. Be careful, as this drill can hurt you.

Continue down the path until you reach two fans. Break the fan that ISN'T working and go through it.

On the other end is a switch. Hit it to be sent flying upwards. Ensure you go forward when sent up to land on the water UNHARMED. Landing without doing so will result in significant fall damage.

Once in the water, kill the waiting wasps and a Serpent.

Head for the big steel door to end the level.