Just played Splinter Zone after some days of vacation and computer-free time. And it still is fun! :)
What I like:
More enemy types. More levels and unexpected turns (I dropped into a pit and below it was more of the level), awesome idea! Also the "being exhausted"-animation is cool.
What I don't like:
For me the game is still challenging, but I'm not sure how it might be, if I know all the different levels... it will still take some time to get to know the ememy spots, the difficult places and more, but I'm not sure if the "oh, just one more time"-feeling will stick. I hope it does. Same applies for the music. Maybe additional songs (each per "level" type) would be sufficient?
- You said, that you will work on the menus. Maybe you can add another option called "Enemy gallery"; where you can see every enemy with it's name and his animation?
- I like the trainer-menu, maybe you can implement it forever, but it only opens up, if the left button on the game pad is pushed at the start. Or it will open, when you do the Konami-Code in the menu (https://en.wikipedia.org/wiki/Konami_Code). And if you want to stick to a true hacker-demo from the Amiga, two things might be help "credibility" > Move the cursor with the mouse and exit the hacker-demo with a right click of the mouse. This was, how most of the hacker-demos on Amiga worked (at least the ones I know).
- If there is an "unwanted" option-set (I do not know, if there is), which might break the game, use it as an option to create a "TILT"-screen, which is shown as soon as you select these options.
- When you enter a boss-stage, there is always a short amount of time, where I wait for the boss-fight to start. I guess this is a valid setting, that it takes a little time. However to make the player a little bit more aware, how about to words, which appear during that "waiting time". The first one is the name of the boss, and then the word FIGHT and then it starts.
- Not sure if this is difficult, but maybe some more "movement" in the background (turning fans, "thick things" moving through pipes... like they do in the cartoons). It would give the game a more polished look and not everything that moves has to be an enemy. :)