Gravity and pressure levels on Jupiter are very high so I imagine any invaders from that planet would be rather like this game - i.e. very flat! Perhaps they are merely from a Galilean moon, but I digress. Actually the appearance of the game isn't too bad, despite the fact the default non-BRIGHT white was kept as the in-game background. At least the alien invaders look imaginative and non-standard to say the least.
The game looks like an inverted Space Invaders clone (with your ship at the top instead of at the bottom), but it isn't. The fluid gameplay of the standard arcade clones is completely absent here, for we have an INPUT statement in the main game loop. The idea is that you type in a number between 1 and 99, and this then manually aims a laser beam at the invaders. Well it looks like a laser beam, but it's actually referred to as a "shell" in the game itself.
Problem 1: You only have fifteen shells but there are typically between 18 and 24 invaders (it varies) in the invasion fleet. So you never have enough shells to win the game outright. All you can achieve is a "very good shooting" message if you manage to take ten or more of them down, however even this will not have stopped the entire fleet. Sometimes more than half of the fleet still remains. Not very satisfying. I feel most players usually want to see total destruction of the invading fleet.
Problem 2: A random factor is added to your horizontal range so that even if you keep typing the same targeting number in, the weapon will in fact hit a different, unpredictable area on any given row each time. That's the skill factor removed then!
Problem 3: If you use any targeting value in the range 73-99 you get no firing at all with the message "faulty shell". This is hard coded into the game, but the instructions don't mention this feature.
Problem 4: Having a game that looks very much like a fast action arcade game but really isn't can only lead to a frustrating playing experince.
Verdict: Should have been called Invaders from Uranus.
