Astro Invader

Using buttons to move left, right and fire, you attempt to ward off invading aliens and their flying saucers. The aliens are dropped off from a saucer and stored in multiple columns until a column is full, then the aliens in that column descend, one by one, and attack. Also, the saucers sometimes descend to attack; if they are not destroyed, one ship is lost.

General: On odd numbered boards, the ships come out in a back and forth pattern. On even numbered boards, most of the ships come out and drop down shafts on the side where the players ship is, thus making even numbered boards more difficult.
Like other shooter type games, you are only allowed to have one shot on the screen at a time. Firing timing is more important that mindless, quick firing.
Simple Strategy: The numbering of the shafts for the explanation below: ***12345***67890***
Your basic strategy and priority is to keep the shafts in the middle of the screen as empty as possible (numbers 4, 5, 6 and 7). This allows you to stay in the middle of the board safely, while the ships fall to the left and right. If you keep these shafts as empty as possible, it is very easy to stay in the middle shooting the ships that fill those shafts, then sliding over to hit a saucer, and returning to the middle.
Saucer Values: The values for the saucers are not random, but are determined by the shot number you are on. 400 is the maximum score, with scores also of 300, 200 and 100 possible.
Counting Shots: I recommend only counting shots on odd boards. At the very start of the game you want to hit the first saucer (coming out in the middle) on the 15th shot to score 400. After that, you want to hit the saucer on every 16th shot to score 400. Your total count, not just the count between hitting saucers is used for your score (Ex. If you hit a saucer and score 400, then hit the next saucer on 15 shots you will score 100. You wil then need to hit the next saucer at 17 shots to score 400 on that one). In other words, if you fall behind on your shots, you need to catch up. That sometimes is hard to do because you have just enough time to shoot 16 shots between saucers, so you want to refer to the following scoring chart below:
If you just scored a 400 on a saucer, here is your score for the following saucer based on the number of shots:
Number of Shots Score
4 200
8 300
12 200
16 400

Everything else in between is 100. So, if you just hit a saucer and scored 300, you could hit the next saucer on the eighth shot to score 400. Or if you have a score of 200, and hit the next on 12 shots, you will score either 300 or 400.
When you hit a saucer and score 100, and you do not know where you are “in the count”, then trying hitting each successive saucer on the 15th shot to try to find a 200, 300 or 400 score.
Counting shots and getting 400 on every saucer increases your score much more rapidy!
WHERE THE SAUCERS COME OUT: The pattern for where the saucers come out is not random either. This pattern repeats and starts at the top each time you get killed. (C- Center, L- Left, R-Right) The spacing helps me memorize it: CLR CR CL CC RLC RR LL.
The saucers always come out at the same frequency, so you can mentally time it to figure out about when they are coming out, then by knowing where, you will already be in position to hit it! You might think that if you know where they are coming, you will want to “camp out” on that side on even boards, but this is a bad strategy because most of the ships will also be falling on that side thus making it very difficult to stay alive.
On even boards, you want to keep the middle of the screen rows clear, and even concentrating on the opposite side of where the saucer is going to come out. Then when the saucer appears you can easily slide over to the other side, and there should not be many ships falling. I usually time my approach to the other side to when there is a gap of ships falling there.
Although all the screen colors are generated by the game’s hardware as opposed to a screen overlay, there are varying bands of color dependent upon where the aliens are displayed vertically. At different heights, the aliens and their saucers are displayed in various colors. When a player’s ship is destroyed, the entire display is drawn in red.

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