# Prime Shooter

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And for those who just cannot get enough math, the following was submitted by JIG reader, Hanoj:

The numbers are falling! Fortunately, you've got the fundamental theorem of arithmetic on your side!

In Prime Shooter, a math game of prime numbers created by Philip Dorrell, press [P] to destroy prime numbers directly, or press 2, 3, 5, 7, E, T, S, or N to reduce composite numbers by dividing them by prime factors less than 20 (E for 11, T for 13, S for 17, and N for 19). Each number you destroy scores you one point, and the numbers get larger and fall faster as your score goes up.

Tip: When fighting off a 256, shout "two two two two two two two two!" in a high-pitched voice, so that "two!" rhymes with "pew!" It won't help you win, but it's fun to say.

Play Prime Shooter

Great find! Way to go other Jonah!

The only thing missing is a pause button (and maybe a nicer look)

Great game! I'd like to use with the pupils that I teach but they may be a little young for this speed of game. If you ever find yourself with a few spare hours with nothing better to do - is there any chance of adding a 'slower' or easier level suitable for Junior pupils? Many thanks.

Jay: Whoa. I totally didn't realize that what I was writing in the form would actually be the review. That was a surprise.

Jonah: Curses, I've been spotted.

Huwjos: I don't know that the creator of the game reads these comments, but you might email him with your suggestion. In the meantime, this is a good alternative for students.

Also, this totally deserves a walkthrough, no?

Hahaha! Walkthrough, indeed.

Ok, here's mine...

Press [P], [2], err i mean [3], no i mean [7], er, uh... [fail].

Although I included it in the tags, what may be interesting to note is that this game is made using 100% DHTML. No Flash. :)

I'm not sure how well it runs on slower computers, though, now that I've got a supercomputer. So, those still in the dark ages of computing will have to report on their technology-challenged experience with it. ;)

(sorry, was that rubbing it in just a tad?)

oooo... supercomputer :P

I liked the idea of this game, but the hardest part for me was trying to fire at the numbers...
I had to move the paddle with the keys, then scramble to find which key i wanted to press (2, 3, 5, 7, p, e, t, s.).... I think it would have been better if there was a different button layout/did not have to move your paddle....

jay's walkthrough helped, though I think [2] [3] [2] [p] gets you a few more rounds in the game before the inevitable [fail] ;)

While it's consistent with the theme, forcing me to use only prime numbers in my shooting makes numbers that are divisible by 2^4 (16) or higher powers of 2 a pain to deal with if I cannot off the top of my head remember any other factors (also on the occasions that 2 *is* the only factor; 64 anyone?). Like the Dr. Who game a while back with the incredibly slow and not-terribly-dangerous robot enemies in the base attacks, it may be consistent with the theme but it rather detracts from the gameplay. The idea is neat, though, and other than this gripe the game is good.

Fun game; I'd have two suggestions for improvement:

1: allow more than one projectile on screen; maybe increase the number as the 2nd or 3rd root of the player's score, it would certainly make those 64s and 96s less trouble.

2: Alternate control schemes! Requiring a player to cover the entire keyboard (from 2 and W to P and then the arrow keys) at the same time as factoring primes is a bit much. My ideal controls would either use G and H for paddle movement or else integrate all keys except the movement arrows into the 10-key pad. Or just a user-defined option. ;)

this one really didn't do it for me. it seemed flawed in several ways. why?
1. if you fire the wrong number at a block (for example, firing 3 at 26), there is no penalty. there really needs to be a penalty, or else it's just fire numbers until something hits and makes it disappear.
2. if a block reaches the bottom without being destroyed, there is no penalty. again, there should be a penalty here, or else you could just dodge the hard numbers and shoot a P at the 3's and 7's falling your way.
as much as i enjoy math puzzlers and the mental challenge i get from them, this one didn't do it for me. not that it wasn't challenging, but once i found out that it could in fact be un-challenging (by taking advantage of the above flaws), the game just fell apart for me.

art:

1. To me, there *is* a penalty for firing the wrong number at a block; wasted time. If you move under a block that's coming down fairly soon and fire the wrong number at it, you have to either wait and hope you can shoot the right ones fast enough to clear it before it lands on you, or you have to move out from under it, which runs the risk of it turning red.

2. There *is* a penalty here as well, but it's not exercised enough. When the blocks turn red and hit the bottom, then you will lose a life. It seems like only one block at a time gets red after falling through, though, which is probably why it doesn't seem to you like there's a penalty, and you probably went after the red blocks pretty quickly anyway.

How far did you get before the flaws made you decide to quit?

ben, that's a good point about the wasted-time penalty. i never really considered that. what would probably work better (in my mind, at least) is to maybe lose a life for an incorrect firing (thus, to balance the difficulty, it might be necessary to start with 5 or more lives), rather than just losing time.

i only got to about 100 points before i quit. do the red blocks start after that, i assume? maybe i'll have to give this one another chance.

As an aside - a real 'walkthrough'.. :)

2 - p

3 - p

4 - 2,2

5 - p

6 - 2,3

7 - p

8 - 2,2,2

9 - 3,3

10 - 2,5

11 - p

12 - 2,2,3

13 - p

14 - 2,7

15 - 3,5

16 - 2,2,2,2

17 - p

18 - 2,9

19 - p

20 - 2,2,5

21 - 3,7

22 - 2,11

23 - p

24 - 2,2,2,3

25 - 5,5

26 - 2,13

27 - 3,3,3

28 - 2,2,7

29 - p

30 - 2,3,5

31 - p

32 - 2,2,2,2,2

33 - 3,11

34 - 2,17

35 - 5,7

36 - 2,2,3,3

37 - p

38 - 2,19

39 - 3,13

40 - 2,2,2,5

41 - p

42 - 2,3,7

43 - p

44 - 2,2,11

45 - 5,9

46 - 2,p

47 - p

48 - 2,2,2,2,3

49 - 7,7

50 - 2,5,5

51 - 3,17

52 - 2,2,13

53 - p

54 - 2,3,3,3

55 - 5,11

56 - 2,2,2,7

57 - 3,19

58 - 2,p

59 - p

60 - 2,2,3,5

61 - p

62 - 2,p

63 - 3,3,7

64 - 2,2,2,2,2,2

65 - 5,13

66 - 2,3,11

67 - p

68 - 2,2,17

69 - 3,p

70 - 2,5,7

71 - p

72 - 2,2,2,3,3

73 - p

74 - 2,p

75 - 3,5,5

76 - 2,2,19

77 - 7,11

78 - 2,3,13

79 - p

80 - 2,2,2,2,5

81 - 3,3,3,3

82 - 2,p

83 - p

84 - 2,2,3,7

85 - 5,17

86 - 2,p

87 - 3,p

88 - 2,2,2,11

89 - p

90 - 2,3,3,5

91 - 7,13

92 - 2,2,p

93 - 3,p

94 - 2,p

95 - 5,19

96 - 2,2,2,2,2,3

97 - p

98 - 2,7,7

99 - 3,3,11

100 - 2,2,5,5

101 - p

102 - 2,3,17

103 - p

104 - 2,2,2,13

105 - 3,5,7

106 - 2,p

107 - p

108 - 2,2,3,3,3

109 - p

110 - 2,5,11

111 - 3,p

112 - 2,2,2,2,7

113 - p

114 - 2,3,19

115 - 5,p

116 - 2,2,p

117 - 3,3,13

118 - 2,p

119 - 7,17

120 - 2,2,2,3,5

121 - 11,11

122 - 2,p

123 - 3,p

124 - 2,2,p

125 - 5,5,5

126 - 2,3,3,7

127 - p

128 - 2,2,2,2,2,2,2

129 - 3,p

130 - 2,5,13

131 - p

132 - 2,2,3,11

133 - 7,19

134 - 2,p

135 - 3,3,3,5

136 - 2,2,2,17

137 - p

138 - 2,3,p

139 - p

140 - 2,2,5,7

141 - 3,p

142 - 2,p

143 - 11,13

144 - 2,2,2,2,3,3

145 - 5,p

146 - 2,p

147 - 3,7,7

148 - 2,2,p

149 - p

150 - 2,3,5,5

Darn it, that spoiler worked fine when I previewed it.. Jay, can you add br tags after each number, please?

art: When you start, let the first block touch the bottom of the screen, then watch as it comes back; it should be red now. Then let it hit the bottom; it should take a life from you. As I said before, this doesn't happen to every single block that goes through the bottom of the screen, which makes it seem like it's not happening nearly at all if you keep a good pace going.

Okay, on second try that seems not to work either; very strange. It's almost as if there's only a *chance* that stuff 'super-activates', which is obviously baloney. The game would work just fine if you were only guaranteed a single extra chance to destroy a block (or none at all, as art desires).

Nuts, I read the site and it is only sometimes that that happens. You probably didn't let too many blocks reach the bottom as it was, and the difference isn't easy to see so it's totally understandable that you wouldn't pick up on their existence. I agree that that constitutes a flaw in design, and though the little breathing room intended to be gained by allowing a slip is nice, making it possible for that to be a lot of breathing room detracts from the challenge. Also, what would probably satisfy your desire is not penalizing misses by causing such to outright harm you, but simply increasing the speed of the blocks such that if you do make a mistake you run a more serious risk of waiting too long to move for a chance at shooting the block again.

Real walkthrough:

Number n: for divisors up to floor(sqrt(n)), test all numbers where
(n / ((floor(sqrt(n)) + 1) )

Otherwise you might - hint! - try to the Pollard p-1 factorization method.

It seems that the easier the number is to factorize, the more quickly it "super-activates". I often found that if a number turned red after only one fly-by, it was almost certainly already prime.

427 on my likely only try -- can't imagine going that long again. It never speeds up much, you just start getting three blocks at a time.

More reasonably, it's probably a good idea to know easy divisibility tests for 2, 3, 5, 7 and 11. That way you're really only ever "testing" three other primes.

Ben and art, I can assure you that when you play long enough, the red blocks and the missed primes become really hard to deal with. When I got my highest score (756), I was often juggling four, five or six numbers at once, several of them dark red. It was a 493 (17 x 29, appropriately enough) that eventually did me in.

126 on my best game (all lives were spent getting hit). It would be a lot easier if it could just be controlled with the number pad and arrow keys. The first hundred points were easy, as I could just have my right hand on the number pad and my left hand controlling movement with my pinky on the [p]. Then after a while I found myself either A) glancing down to the keyboard or B) having to move both hands over to the alpha-numeric side of the keyboard to find the key I needed, significantly losing time and forbidding myself of movement.
If this game experiences a second incarnation, I would definitely like to see powerups. Mainly temporary invincibility, slow-motion, instant number eliminator, and the ability to shoot more than one number at once.
Otherwise, it's a very nice and balanced game.

Took me a while to finally figure this one out. Not being as smart as my fellow gamers, this didn't make much sense until I discovered that a prime number is any natural number that can only be divided by 1 or itself. Once that "eureka moment" hit (and the feeling of stupidity subsided), the game became much easier, and certainly, much more enjoyable.

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