UC Berkeley StarCraft Class, Week 5

We started out this week briefly talking about a problem from the homework about marines and medics. If H is the hit points of a marine, t is time, and B is the rate the marines take damage over time, then

H - Bt is the hit points of the marine. Set that = 0 for when the marines die and we can solve for t = H/B.

Meanwhile, let A be the rate at which medics heal marines. H - Bt + At is the equation for marine hit points in this case. Again set to 0 and solve for t to get t = H /(B-A).

The ratio of these two cases (marines only vs marines + medics) is proportional to B /(B-A). Looking at the limits, you can see that as A approaches B, the limit goes to infinity, meaning that marines never die. If A = 0.8B, a value reasonable to achieve in actual gameplay, then the limit shows that marines live five times longer. I think the non-math way of saying this is, "against Zerg, use marines + medics." Zerg units (because they have low hit points) can get rocked really bad by marines that live longer, and in some cases, can't even keep up with medic healing.

Economy

First consider an idealized form of the in-game economy, and the exponential growth it has. Imagine you build probes as fast as you can, and then build a new nexus at every earliest opportunity. You do this because building new nexuses (nexi?) is the only way to increase the rate you can produce probes.

If P(t) is the number of probes you have over time, then the rate of change, d/dt of P(t), is proportional to N*B, where N is the number of nexi and B is your rate of building probes. Also, d/dt of P(t) is proportional to P, the number of probes you have. Or at least I think that's what Professor Feng meant here. Solving these differential equations yields P(t) = A0eN*B*t, an exponential graph.

We then saw an example of of this in action on a ridiculous map called "fastest" which starts with your nexus so close to the mineral patch, that the probes have no travel time. By building only probes, then nexus, then probes, then more nexus, etc as fast as possible, you could see the explosive growth of the income. Of course, there are limits here. You can have only 200/200 supply, each mineral patch has limited number of minerals, lots of probes cannot simultaneously mine a mineral patch, etc. Also, you can't have fractions of a probe mine, and you can't spend 25 minerals to build only half a probe, so the idealized exponential graph is not exactly right, but we can start with it to approximate the real state of affairs.

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Short Story: Exhalation

I really like Ted Chiang's science fiction short story Exhalation. You can listen to a reading of it here, it's about 45 minutes. Don't be scared by the accent of the guy you hear at the start. The guy who actually reads the story has a wonderful voice for the part.

Science fiction (well, any fiction, but especially science fiction) can make us reexamine something by making us look at it from a different perspective. When you're trapped inside a culture or way of thinking, sometimes it helps to escape by asking what an outsider would think of it all. Science fiction has lots outsiders to ask those questions!

I probably shouldn't say much about the story, other than that it's somewhat related to the concept of consciousness, and that it asks about existence itself. Your mileage may vary, but I enjoyed it a lot.

Street Fighter 4 Ultra Combos

Lots of people have asked me why the Ultras in Street Fighter 4 work they way they do. I have no inside information on this, nor have I even seen what the designers might have said, but I have a pretty good guess. After walking you through that, we can then ask if we would include such a mechanic in a new, ideal fighting game. I actually don't know the answer, but I can explain the issues.

When I first saw the ultra system a long time ago, I though it was a terrible, terrible idea. My reason was that the last thing casual players wanted was a SECOND super meter. I mean this isn't Guilty Gear, it's supposed to be simple and elegant, and a new super meter in addition to the old one (which has four divisions and multiple uses) is going to be a confusing mess. I think it turns out there was more to the issue than I thought back then, so let's look at all the issues together and see if the overall effect is good or bad.

But first, let's explore how I imagine ultras came to be what they are in this cartoonized, fictional line of thought:

"How can we get casual players interested in this game? There's lots of ways of course, but one way would be really flash super attacks. Yes, that's a natural answer because we already have had super attacks in lots of other Street Fighter games, and now that we can use 3D animation, camera movement, and effects, we'll be able to make these look even better than ever. So far, this sounds great."

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Some Positives About Street Fighter 4

Yeah there's a lot of problems in SF4, but there are some good things too.

I don't know how effective Gouken is, but his design is interesting. No dragon punch, but a super and ultra dragon punch. A high counter and low counter that act somewhat like a dragon punch, but worse because he has to guess high or low and it loses to the "breaking glass" moves, like Cammy's cannon spike. The ex counter doesn't require you to guess high or low though. I beat Cammy's ultra once with an ex counter, but got hit the second time I tried. Not sure what's up with that. Also, using the counter drains your life and slowly refills it, like using a focus attack. This is an advantage for the most part, because it means your ultra guage is even more full than usual. Because his ultra is guaranteed off a normal throw (and easy), it's basically a throw super...that doubles as the occasional dragon punch super if you really need it. Ironic that landing it is so easy that it's a better "throw super" than Zangief's, at least for me.

It's painful dealing with Zangief's bad-feeling jump, as if he is a flea of some sort, and not having his hop move. And not having his low fierce from Alpha 2 and 3. But his SPD is good, with jab having ridiculously long range (great!) but low damage. SPD startup time is

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A Few Things About Street Fighter 4

Street Fighter 4 is finally here, with several perfect 100/100 reviews. Here's a few things I noticed about the game.

In ranked matches, you can see the opponent's name before the match and kick them or reject the challenge. This allows you to cherry pick who you fight and negates the entire purpose of a ranked match.

In ranked matches (well, all matches) there is no double blind character select. This means the optimum strategy is often to wait until the opponent chooses first so you can counter-pick. This is a very annoying situation.

When lag inevitably happens in an online fighting game, there are different ways to handle it. Some SF4 matches I played had large input delay,

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