Messed with Atari 5200 Robo port this week (same as the Atari 8-bit computer port).
It was like playing Robotron with Mario from the Atari 2600 Donkey Kong.
I'll list some observations.
Nothing at all like Atari 7800 version which is so close in enemy dynamics that you play it with same technique as arcade and scoring/waves are approximately the same as real arcade. It has the essence of robo where gameplay is balanced so you can always redeem yourself or maybe get out of a tight spot with some skill and luck.
The enemy dynamics are way off in 5200 so you have to play it with different technique.
The game is almost imipassable by wave 35 due to ridiculous lightning bolt missile quantities.
The game is choppy so you have to make any moving projectiles a priority. If the screen fills with projectiles from enforcers/tanks/brains it is quick death.
Spheroids tend to head to bottom edge of screen and to right so kill them first
Always move to the right and down otherwise a kamikaze will get you before you can move away.
Then get quarks before they make tanks, by shooting across screen straight or diagonal full length of screen.
Then you can kill grunts with straight line firing and try to save a last grunt so you can run around to get humans.
running diagonals makes the player faster so grunts are never a problem in the waves.
Humans are fast and tend to run toward hulks.
lightning bolts are manageable on wave 5 but after that they are near impossible to get shot out of the air and they bee line to kill you with no way out.
If you get stuck with a lot of tanks you have to go to a vertical wall and straight shoot to survive it. it takes diagonal long shots to get the last quark which will run from your shooting effectively.
Kamikaze death is common by quarks on tank waves unless you can get to an edge with straight line shooting.
On default difficulty 1 I was able to reach wave 36 at 480Kish
on difficulty 0 I had one game to wave 65 at 860Kish.
Mostly wave 35 ends all games since you have to kamikaze into brains until they are gone which takes about 5 lives.
Summary-not fun at all. N64 version might be busy and hard to visually discriminate but at least it is fun and has more essence of robo than the 5200 version.