Pros:
Graphics: The graphics of this game make it pretty clear and suit the game
Controls: Just the [2nd] and arrow keys
Gameplay: Fun to play and has a high score table, so you can try and get a higher score every time. My high score is 2723.
The game has very smooth gameplay and scrolling.

Cons:
Repetitive Play: The level is the same thing over and over again. You fight through several enemies and the whole thing starts over again. It is just the same sequence of events over and over until you die.
Playing for the first 20 times: This game is very difficult to play when you are a beginner. You will die a lot, and it won't be fun. But the important thing is to develop a pattern to dodge the bullets, because the enemies shoot in a similar pattern each time.

Obviously, this is a demo version, so giving a full rating would be unfair. Instead, I'm going to tell you my initial thoughts about the “Zmercury”.

There are a few things that seem evident when playing this game. The most obvious is that it is much faster paced than many other games of this nature, and ten times as hard. The enemies (and your own character) are huge, making it near impossible to dodge enemy fire, and nearly impossible to miss. This is where (in my opinion) the game suffers. This may just be because it is a demo, I'm not sure. But to me there is no fun in this game because you can't really do anything to avoid the constant fire coming at you.

Disclaimer: I was one of the beta testers for this program, so my views may be slightly biased. All attempts to mitigate the effects of such bias have been made while writing this review.

“ZMercury” is an excellent port of the revolution “Mercury” for the 68K calculators (that is, the TI-89 (Titanium), TI-92, TI92+, and the Voyage 200), also written by Patrick Davidson.

Playability: This is the first release of “ZMercury” for the TI-83+/TI-84+ calculators. Therefore, it is rather short right now. However, it is still playable due to the high scores list. I have no doubt that it will get longer in later releases. Rating: 8/10

Graphics: “ZMercury” retains the high quality graphics and the high frame rate of “Phoenix.” While it is not grayscale, the black and white graphics are good enough. Rating: 10/10

Stability: There are no bugs with the program yet (there weren't any bugs in the beta version either). The high scores bug was fixed before I started beta testing the game. “ZMercury” is completely stable and should not crash your calculator, given that your know how to use it. Rating: 10/10

Features: Again, the lack of features is attributed to the fact that this is a first release. I count only four types of enemies and one type of weapon. However, that is already very impressive for a first release. Features: 8/10