Level 28: All Roads Lead to Sol...
This is the final level - and helpful hints are few and far between. Suffice it to say, this is a level where you are mostly left to your own devices.

As you arrive - save the game, arm yourself and recharge. Then head down the right hand staircase. You'll soon come to a location where the walkway around the lava is missing - hit this switch to rectify that situation.

You may have to swim (i.e. you will) to get to the switch that controls the door at the far end of the lava walkways...

After opening that door you'll find yourself in a very strange room.

This room houses the lava control switches. Open the panels and blow away all of the control circuits behind them. But, shoot the ones closest to the door first... as the exit door rises along with the lava, jump out and swim back to where you started.

As you can see from this map the lava has now shifted from one side to the other. Run on down the stairs and do battle with the foes that lurk below.

Another view to help you out... After this stage you'll find a 3x re-charger and two Juggernauts. Do battle with them and then swim the entire length of the pool. At the end you'll find another 2x re-charger and some stairs. Up these stairs there's a teleporter that takes you to the final level... 'nuff said.