Level 1

Secret: 1 -  When you dive into the water for the first time, head right
and then left until you see an opening above you. When you emerge behind
the wall, you'll find some armor shards and a grenade.

Secret: 2 - Look under the stairs on the left side and you'll see you
can crouch underneath to grab the Silencer.

Secret: 3 - Behind the elevator and stairs, look at the ceiling and you
will notice an odd yellow light. Shoot at it to activate the wall
opening. Crouch down to pick with the grenade and health packs. believe
me...you'll need it.

Strategy: 1 - Use your blaster to light up dark rooms.

Strategy : 2 - Shoot at explosive containers to help gib the enemy.

Strategy: 3 - Crouch down to get this armor, and continue along until
you're above some guards. Fall backwards to face him dead one for an
easy target.

Strategy: 4 - Also shoot at explosive containers to blow holes in weak
walls and floors - such as this case, here.

Strategy: 5 - Look up when you enter tall rooms with multiple levels -
there will usually be enemies firing at you. Also, try to fight the
tougher aliens one at a time or they'll fill you up with tons of lead
before you know it.

Level 2

Secret: 1 - Shoot at any odd-looking walls to uncover secrets like this.
Pick up this shotgun and keep going.

Secret: 2 (after completing level 3) - Drop down behind this wall to
uncover an underground secret area with ammo, a weapon, and health.
Watch out for guards the moment you touch the goodies.

Strategies: 1 - Touch the button on the wall to snag the machine gun.
This is a great weapon to have on your side.

Strategies: 2 - Remember to watch for the guards to plow through the
wall here. The Strogg like to hide so listen carefully for any audio
clues.

Strategies: 3 - Collect all these goodies to help you along. Fall down
onto the health (on top of the crate) if you need it.

Level 3

Secret : 1 - Find the crack in the floor under the water and crouch down
into the crevice. Turn left and walk underwater until you see an opening
at the top. emerge into a secret area with health, ammo, and another
weapon. You can either turn back and go out the way you came or enter
the hidden level of unit 1.

Strategies: 1 - Parasites like to lurk in these dark areas of the floor.
Aim for them before you even see them to get the all-important first
shot.

Strategies: 2 - Jump up on these containers to access the quad damage on
top of the crate.

Strategies: 3 - At a distance, blow up these striped explosive boxes to
help clear out the room.

Strategies: 4 - Jump onto the crate from above that has the Enviro-Suit
on it. this will prove handy at a later time.

Strategies: 5 - Watch for the Parasites to blast through the walls on
the right (didn't you learn anything with those guards!?). Enter this
small hole in the wall to snag some ammo.

Strategies: 6 - Complete the uplink to the Terran mothership. Once
you've cleared the room, touch the computer display to activate the
satellite transmission. Pick up the blue key when it surfaces from the
floor beside the computer terminal.