🚀 go-pugleaf

I have solved the entire thing, but its not easy.  That guy is the hardest 
one in the whole game, including the guy at the end of level 27, because 
there are a zillion invulnerability powerups there.  Anyway, here's how I 
did it (After losing about 50 ships).  Run down to the last room and go 
through the door, but don't go in very far, shoot a few shot, and come back 
out.  See if you can lure a few of the bad guys right in front of the door 
so you can kill them without having to enter the last room (and get stuck 
there).  Alternatively, you can just peek around the corner and shoot at 
them to kill as many as you can.  (They can't get you if only the tip of 
one of your guns is sticking around the corner).  There are a bunch of 
goodies scattered around that room, but don't bother with them, you'll most 
likely get killed trying to gather them up, although if you could make it 
to the invisibility powerup at the bottom of the pit, that might help you 
collect some shields, IF you can get to it!.  Find the laser energy 
recharging spot, and kill all the guys except the big one from that 
"safe zone".  Then wait in there until the big guy shows up. (He can 
dematerialize and show up some other place at will, so stereo speakers will 
help here).  If you're luck and wait long enough, he'll show up just below 
your field of vision outside of the tunnel.  If this happens, you're in 
luck, because he won't be able to see you, but you'll be able to hammer 
him.  Shoot like mad with everything you've got.  He'll probably disappear, 
but you can just sit back and wait for him to show up again.  If he happens 
to show up right in front of the tunnel, high tail it out of there and run 
around the sides to avoid those seekers, but with practice, you should be 
able to avoid them and make it back into the charger.  Eventually, he'll 
start spinning around and die.  Good Luck.  You might want to get to know 
the room using the cheat codes first (instead of wasting 50 ships like I 
did).  They are, in case you don't have them yet:
GABBAGABBAHEY - enable cheats
RACERX - invulnerability (fo about 10 minutes)
GUILE - invisibility
BIGRED - all weapons (only in the registered version, I can't remember the 
one for shareware)
FARMERJOE - level warp
Good Luck!