Bah, a lot more effort could have put into this.
There doesn't seem to be much of a plot to this game. You seem to be defending various bases against alien invasion. The levels are situated on Io, Ganymede, Callisto, and Europa (Jupiter's four moons), and then Jupiter itself. Each level consists of 10 "waves" of enemies, most of which are followed by a "wave leader". At the end of the 10 waves you battle the "planet guardian". The enemies come in various shapes and sizes including floating things that drop mines, bombs which explode, and little green Space Invader-esque things. There are three different types of wave leaders that seem to loop. Each planet guardian itself is different.
The graphics are nothing to write home about. They could possibly pass for NES graphics just before that system became defunct. The backgrounds for each planet are somewhat similar, but with slight variations, and like I said the character graphics look like enemies from a NES/SMS game.
The sound is pretty poor as well. Simple shooting noises are the best this game gets and when it tries to make explosion noises and speech it just sounds very fuzzy, and for the latter, almost incomprehensible.
The gameplay is also simple. As previously mentioned each level is divided into 10 waves. you must defeat all enemies in order to advance to the next wave. You have a variety of weapons to use, but you must pick up powerups from the enemies to use them. Aside from your standard gun you can pick up an automatic weapon which just requires holding the button, homing missiles, and two spheres that surround the player, protecting him. As for the rest of the controls, one button cycles through the weapons, another turns the player transparent and immune to damage (this uses a finite energy source), and one detonates a bomb that damages all enemies on screen. The player is controlled via their jet-pack, pressing up to rise and left and right to zoom around. Being in space, however, means that after you stop pressing the button your player will continue to move and you must press the opposite direction to slow down and stop. The level design itself is also very simple and very repetitive. Gets boring very quickly.
As for the lastability, well it is a very hard game to finish, but it is also quite boring. So it will either take a while to finish with perseverance, or you'll have switched it off within 20 minutes.
Overview
Graphics: Very dated for year of release. Looks like previous generation
Sound: Also very poor. Simple sound FX and garbled speech.
Gameplay: Varied weapon options, but fidgety controls and hardly any variation between levels makes a boring game.
Lastability: Game is very hard, will take a while to finish, but game is so frustrating it takes some perseverance.