Final score: 115,100
I didn't pick up Xybots until I was in college, and I've never had much time to sit down with it and play more than 20 min or so...until tonight. Brilliant game. The difficulty really ramps up around level 18 or so. The Xybots start moving around the maze on their own, and they shoot at you before you're close enough to see them. The levels open up so that you're fighting in big rooms instead of cramped corridors. And you start getting into shootouts with more than one enemy at a time. The hardest thing about the later levels is that your energy doesn't refill after each level, so if you clear a level with 6% energy, that's what you'll have when you start the next one. This makes it really important to save your cash for the later levels. The earlier levels are easy enough that you really don't need stuff like faster walking speed, more powerful shots, or higher energy limits.
Some tips:
As early as this game is, you can use the same tactical "room clearing" strategies as in modern shooters like Call of Duty. Instead of walking around a corner and then turning to see what was hidden from you, you'll be safer strafing/sidestepping around it. In other words, if you're walking down a hallway that bends to the right, instead of walking forward and then turning to the right, you should face to the right, and then sidestep to your left so that you can see what's around the corner as soon as possible. If you're coming to the end of a hallway where there's open gaps to your right and to your left, you're best off doing a "quick peek" in each direction. Turn to your right, strafe into the new area just far enough to see what's ahead, then strafe back the way you came. Turn around, clear the other direction, and then you'll be safe to explore further. That way you won't be ambushed by an enemy hanging out in a corner behind you.
Always keep your Slow Energy Loss maxed out. Energy is the most important thing in the game, as it's a combination of your life and your timer, and the game ends once it's gone. Always keep an eye on your energy percentage.
Energy capsules will give you either a 50% boost or a 100% boost. Never pick one up if your energy is over 50%, unless you're heading right for the level exit.