Details

I hope I have enough detail here that it looks authoritative, but don't be fooled, it is just some stuff I gathered by observation. It could be wrong.

I'll start with some general facts about the game that I left out before, then move on to discuss each of the “things”, or units, in more detail.

Levels

Probably the most important thing that I left out is that the level colors aren't just decorative—the whole character of the game depends on the color. On the blue levels, flippers, tankers, spikers, and fuseballs are gradually introduced; on red, pulsars appear; on yellow, multiple fuseballs appear; on cyan, the pulsars speed up; and on black, they speed up even more, and of course the grid lines aren't visible. Then, on green, there's no obvious single change, except that you can see the grid lines again.

It will be helpful to have letter codes for the different colors involved. I'll use RGB for red, green, and blue; CMY for cyan (light blue), magenta (purple), and yellow; and K for black.

In Tempest, as in many other arcade games, when you lose, if you put in another quarter within about 30 seconds, you can continue where you left off, more or less. There are certain levels that act as ratchet points, and after you get past one, you can start there. Here's a table of the ratchet points.

B	1		3		5		7		9		11		13		15
R	1			4		6		8		10		12			15
Y	1			4				8				12			15
C	1			4				8				12			15
K	1								9
G	1

Unlike the other arcade games, however, in Tempest you can choose which of the ratchet points you want to start at. The way that works is, when you start a game, the ratchet points are displayed as a row of icons, like so,

and you have 10 seconds to flip through and pick the one you want. Of course usually you want to start at the highest one, but you're not required to. And, even if you're starting from scratch, you always have access to the points up to B9.

As above, it is often convenient to identify levels not by an absolute number but rather by a color plus a number N between 1 and 16 that tells the shape. Many properties of the levels are determined by the shape. For example, on levels where N is 4 or more, the surface starts out with small spikes on all the panels, even if the level doesn't actually include spikers.

One of the things you learn in topology is that all one-dimensional shapes are essentially either lines or circles. (The exact statement is left as an exercise for the reader.) The level shapes in Tempest cover both possibilities: some levels (8–11, 14–15) are linear, the rest circular. You wouldn't expect it from the picture in the previous essay, but the number of panels a surface has is determined solely by topology: linear levels have fifteen panels, circular levels sixteen. In the triangle (N = 6), for example, the bottom side has six panels instead of five.

Dots

Another thing I left out has to do with dots. When you start a level, there are a bunch of little dots swirling around (counterclockwise) in the empty space beyond the bottom of the surface. As the dots swirl, some of them stick to the surface, and then, sooner or later, depending on how many units are already on the board, they emerge as new units and proceed upward.

The reason the timing varies is that there can be only a certain number of units on the board at a time, the exact number depending on the level. So, early on, the dots can emerge right away, but mostly they have to wait until you kill something.

So, most of the time, the total number of units is conserved. A lot of the time, the number of each type of unit is conserved as well—if you kill a pulsar, the next dot will emerge as a pulsar, or perhaps as a pulsar tanker on higher levels. That's not always true, but it is a good rule of thumb.

(I'm quite certain there is something more to be learned about when the types are and aren't conserved, but I don't have it figured out well enough to be able to say anything useful.)

One thing that maybe I haven't made clear is that the number of dots is finite, and tells how many things you have to kill to finish the level. You might think, then, that the number of dots always decreases, but that's not strictly true—if you die, the units on the board turn back into dots. The thing that always decreases is the number of dots plus the number of units. Nevertheless, it is the number of dots that controls when the level ends. As soon as the dots have all emerged, it becomes possible to finish the level without killing anything else, and that brings me right to the next point.

The Endgame

When the last dot emerges, the endgame begins. The units all come up to the top of the surface, and if you can stay alive until they get there, you win, and get to move down the surface and on to the next level.

Of course, as I said before, if you run into a spike, you die and have to try again. On the first few levels with spikes (levels B4–B7), the game displays the catchy warning AVOID SPIKES and gives you a second or two to move around to a good spot, but on higher levels you just start accelerating.

Even after you've started accelerating, you can still move from panel to panel. You can also still fire and wear down the spikes. On the early black levels, you can wear down the spikes fast enough that you don't even need to move around, but most of the time you need to find an open panel, or at least one that only has a short spike.

If you die during the endgame, whether because of a unit or a spike, the units on the board (if any) turn back into dots, and the endgame doesn't resume until they've all emerged again. That doesn't take long, but it is not instantaneous.

What makes the endgame distinct from the rest of the game is that the behavior of some of the units changes. In fact, it has to, otherwise the units would never reach the top of the surface.

• Flippers and tankers don't do anything different.
• Spikers continue as usual, except that now when one reaches the bottom and jumps to another panel, it also turns into a tanker (a flipper tanker).
• Fuseballs, in the endgame, finish crossing whatever panel they're on, then come straight to the top and converge on you. This is troublesome. Basically, if you're on a level with multiple fuseballs and you haven't saved your super zapper, you die.
• Pulsars continue as usual, too, but now they come all the way to the top, and when they get there, they act just like flippers. In fact, for some mysterious reason, about half of them actually turn into flippers. Also, pulsars that were moving downward turn around immediately, instead of going down to the usual turning point. That change is the earliest sign that the endgame has started.

Units

Before I start on the individual units, here is some general information. This first table shows which unit types appear on which levels.

board	B	R	Y	C	K	G
flipper	1	1	1	1	1	1
tanker	3	1	1	1	1	1
spiker	4	4	11	1	1	1
fuseball	11	6	1	1	1	1
pulsar	-	1	1	1	1	1

Fuseballs, for example, first appear in blue on B11, and in red on R6. So, they appear on B12–B16, but not on R1–R5.

This second table shows how the unit colors depend on the level color.

board	B	R	Y	C	K	G
you	Y	G	B	B	Y	R
flipper	R	M	G	G	R	Y
tanker	M	B	C	M	M	M
spiker	G	C	R	R	G	B
pulsar	-	Y	M	Y	C	C

You

I've been using “units” to mean enemy units, not including you, but there are a few points I haven't mentioned about the unit that you control, and this is a good place to put them.

First, the number of shots you can have on the board at once is finite. If you hold down the fire button, you'll get a burst of shots, and then nothing, until one of the shots hits something or reaches the bottom.

Second, the super zapper kills everything quickly, but not instantaneously. If, say, you are about to get caught by a flipper, the super zapper by itself will probably not save you, you'll also need to fire some shots to protect yourself (see below).

Third, when you use the super zapper a second time, to kill one enemy, the one enemy is not chosen randomly. If there are fuseballs around, it usually kills the nearest one, but if you're in the endgame, and there's only one enemy that hasn't reached the top, sometimes it will kill that instead.

Flipper

Flippers flip from panel to panel in one of four patterns, depending on the level.

fall	1													14
spin		2	3			6		8		10		12			15
weave				4			7				11					16
follow					5				9				13

Even on levels with the same pattern, the flippers may seem to behave differently due to different ratios of flip speed versus approach speed.

The “fall” pattern is simplest: the flippers just fall towards you, and don't flip at all.

In the “spin” pattern, the flippers spin around the surface in one direction or another, without changing direction … unless, of course, the level is linear, in which case they change direction when they come to one of the edges.

Actually, it's not true that the flippers spin in one direction or another. When a dot emerges as a flipper, it always spins clockwise. But, after level B4, dots don't emerge as flippers, only as flipper tankers, so you only see asymmetrical spinning on levels B2 and B3.

In the “weave” pattern, the flippers weave back and forth, taking two or three steps in one direction then some number, not necessarily the same, in the other. I think the details are different on the different levels.

Finally, there's the “follow” pattern, which is just like the “spin” pattern except that the flippers will stop spinning to follow spikes. In other words, when a flipper is on a panel that has a spike, it will stay on that panel until the spike ends.

When a flipper reaches the top of the surface, everything changes. It switches to a “spin” pattern, possibly changing direction, and it switches to a different (faster) flip speed. And, since it's at the top with you, and you die if it lands on the panel you're on, you can't exactly shoot it. Fortunately, there is still a way to kill it. If you fire a shot while it's flipping onto the panel you're on, it dies. This is why the different level shapes matter—flippers take longer to flip through larger angles, so it's easier to kill them in some places than in others.

Another thing you can do while a flipper is flipping is scoot underneath it to the panel it just came from. This is amusing, but not very useful.

Tanker

There are three kinds of tankers: normal (flipper) tankers; fuseball tankers, which first appear on level Y1; and pulsar tankers, which first appear on Y9. If you're careful, you can tell the different kinds apart by looking—fuseball tankers have a little four-spoked fuseball inside the inner square, while pulsar tankers have a little pulsar there.

As a rule, when a tanker hatches, it turns into two units of the appropriate kind, one on each adjacent panel. There's a major exception, however, which is that if conservation of units is in force, a tanker can't turn into two units, only one. But, if a tanker is hatching because you shot it, probably you just shot a bunch of other things as well, and conservation won't apply; so the exception mostly applies to hatching at the top.

There's also a rare minor exception, which is that once in a while a pulsar tanker will hatch at the top into two pulsars and a flipper. I suspect there are other, rarer exceptions, but I haven't seen them enough to know.

When a flipper tanker hatches because you shot it, the two flippers start out moving in opposite directions, away from where the tanker was. But, when one hatches at the top, anything can happen. When a fuseball tanker hatches, the fuseballs can appear on either the inner or the outer grid lines of the adjacent panels, and their first move can be either horizontal or vertical.

Spiker

There's not much else to say about spikers. One thing that's interesting is that except on the earliest levels, they move downward faster than you can wear down their spikes, so if you don't shoot them on the way up, you can't shoot them at all.

Another thing is that starting with the yellow levels, there can be only one spiker on the board at a time. And, as with the limit on the total number of units, the limit on the number of spikers leads to apparent conservation: when you kill the spiker, the next dot emerges as a replacement.

If you like thinking about such things, here's a fun question: when a spiker jumps to another panel, is the new spiker really the same as the old one? Or is it different from it, but caused by it? (And in what sense do spikers even exist at all?) That problem reminds me of the problem of object identity, particularly of teleportation and elementary particles.

I was originally thinking that spikers, when they reached the bottom, turned back into dots momentarily, and only reemerged as spikers because of the partial conservation of types. In that case, the new spiker would definitely be different. However, that view has observable consequences, and seems to be false. The problem is, the conservation ought to be partial, and yet, when I've experimented with not killing spikers, I've never seen the number of spikers on the board decrease (before the endgame).

Fuseball

If a fuseball is at the top, moving toward you, and you're on the panel adjacent to it, it won't kill you when it moves through the vertex and heads downward, as it must—unless, of course, it's the endgame, in which case it will stay at the top and kill you after all.

Once in a great while, when I'm playing, I'll be pleasantly surprised to discover that I've just moved through a fuseball and am still alive. How does that happen? I'm not sure. Maybe I catch the fuseball when it's exactly at a vertex, or maybe I move so fast that I don't occupy all the intervening positions. In any case, I can't reproduce the effect reliably enough to bother with it.

Fuseballs have two kinds of behavior prior to the endgame. On the blue and red levels, the single fuseball wanders around aimlessly, and it's just bad luck if you happen to run into it. On the yellow and cyan levels, most of the fuseballs do the same, but there is always a designated chaser, a fuseball that always moves toward you when it moves horizontally, and always rushes to the top if it gets underneath you. Then, on the black and green levels, the fuseballs are all chasers.

Actually, that last paragraph is not absolutely true. I know that chasers sometimes move in unexpected directions, and I suspect that normal fuseballs are not entirely aimless. Nevertheless, there is a lot of truth in it.

Pulsar

Let me start with a couple of fundamental points I glossed over before. First, pulsars flip from panel to panel just like flippers, but they don't have a pattern, they just always move toward you (really always, unlike chasers). Second, they “may” shoot at you, in the sense that you may be on level C12 or higher.

As I said before, the pulsing is periodic; here's a table of how the period depends on the level color. The numbers are only approximate.

board	B	R	Y	C	K	G
period (s)	-	1.5	1.5	1.0	0.75	0.75

Interestingly, the flip speed and the pulse period don't always match up. The number of flips per pulse is usually close to 1, but the exact value depends on the level shape and color. I don't have the patience to make a complete table, but I do know some interesting values: the number can be as low as 2/3 (on K2) and as high as 2 (on Y9 and others).