Vote for Velocity Raptor!

Posted in: Quantum Game, Velocity Raptor | November 5, 2012 | No Comments

Voting for NSF’s science game competition is heading in to the last few days. So go here, register quick, and vote!

In fact, I’ve decided to make a deal. For every ten votes Velocity Raptor gets, I’m going to release a sneak peek at my upcoming Quantum game. It is in development, and has been up to this point fairly secretive.

But you can change that! Go vote, get your friends to vote, and if you’re in the US, show up at your local polling place tomorrow, and ask people if they’ve voted in the election that really matters.

If you check the link, you’ll notice we’ve already hit the first benchmark of 10 votes. So I’d better go get ready to release the first pictures of the game.


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VR is a Finalist!

Posted in: Velocity Raptor | November 1, 2012 | No Comments

As you may notice from the tasteful and discrete button above, Velocity Raptor is a finalist in an NSF competition! Specifically the ‘International Science and Engineering Visualization Challenge.’ A mouthful! (SciVis for short).

And before reading any further (and wandering off into the bushes or some such thing), click the button and go VOTE for Velocity Raptor.

Basically, this looks for great science visualizations. There are categories for photos, videos, etc. One of the five categories is ‘Games and Apps.’ Thanks to the eagle eyes of a friend who noticed this competition going on (my head was off somewhere else, daydreaming about quantum mechanics games, most likely), I submitted. I just heard today that Velocity Raptor is one of the Top 10 finalists in the games category. Yay!

At this point, some judges will take a look at the games and rate them through some magical and mystical process. In fact, I encourage you to do the same. The list of finalists are posted, and many of the games are free/easy to get. So if you like science games (one of the two big reasons to be on my site in the first place), go here to check out some cool ones.

The other big reason you may be on my site is because you know/like/tolerate me… in which case, do me a favor and VOTE for my game. That’s right, in addition to the judges, there is a People’s Choice award that goes out. Voting runs until November 8th. It’s free and easy to do, so go vote for Velocity Raptor!


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Some Changes

Posted in: Gravity Simulator, Velocity Raptor | October 5, 2012 | No Comments

In the past weeks, I’ve made a couple minor updates around here. I went through and updated Velocity Raptor based on some of the comments I’ve received (tough levels, confusion, etc) and also some things I just wanted to improve. (Prettier drawings, mainly) You can see the results yourself!


Velocity Raptor Main

Shiny and New!


And after doing that, I realized that my Gravity simulation could use the same treatment. In spite of the fact that it was one of my first projects, and I have never promoted it anywhere, it gets a fair amount of traffic. I guess people like playing around with planets! So I made some of the drawings for that one prettier, too.


New Gravity

Shiny and New!





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True Bullets?

Posted in: Velocity Raptor | May 7, 2012 | 2 Comments

Thanks to the fine folks over at the xkcd fora, I’m happy to annouce I was wrong about the bullets in Velocity Raptor. I’m even happier to announce that the ‘measured’ bullets have been fixed.

They had been drawn in a way that slanted the bullets away from their true path. Given the argument outlined in April 30th’s post, I thought this was fine. I thought, in fact, it was a demonstration of the Thomas Rotation.

But it turns out this just wasn’t the case. The error in my thought process was that I had LEFT OUT the Thomas Rotation. Two boosts added together can make a boost + rotation. I thought the rotation sprang from my code naturally. But it didn’t. I needed to add that rotation in by hand.

Look how much happier Velocity Raptor is!

So thanks to everyone who brought it to my attention. The ‘measured’ bullets are now fixed in the game. Go enjoy the (now slightly-less) trippy world of Special Relativity.


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What’s up with the bullets?

Posted in: Velocity Raptor | April 30, 2012 | No Comments

That is undoubtedly the most common question about Velocity Raptor. As it turns out, I was wrong. Read the above post for more info…

That is undoubtedly the most common question about Velocity Raptor. And, admittedly, it is counterintuitive. Extremely so. Even and especially for people with a relativity course under their belts. (When I was making the game, it took me a lot of double-checking to feel comfortable with it.) But… we have to listen to the math. We can’t do relativity by intuition alone.

I mention this explanation in the Relativity 101 page, but I think these pictures, and elaboration, could help make the situation clearer.

To understand the behavior of the bullets, we just need one starting point: Length Contraction. If a train is speeding past, a stationary observer would measure it to be shorter than the same train when stationary. And the length contracts in the direction of the motion (the train seems shorter from engine to caboose, not from top to bottom). Not a hard pill to swallow.


As a concrete example about the motion of bullets in the game, we turn to Level 7. Our intrepid hero (Velocity Raptor) finds herself in a room with a cannon. The cannon is firing bullets horizontally across the screen, whereupon they hit a target. VR also decides to run up (vertically upwards on the screen). So we have three frames of reference.


  • That of the Raptor
  • That of the Room, gun, and target
  • That of the bullets

We’ll want to make sure to treat them each independently. For the purposes of this game, we are witnessing the world through the raptor’s frame of reference. So we need to figure out how (a) the room, and (b) the bullets will contract. Let’s start with the room.


Since the raptor is running upwards, to her the room seems to be going down. The direction of relative motion is vertical, so the Length Contraction happens vertically as well. The result is the room seems squished from top-to-bottom. Not a big surprise there.

In the exact same way, we can figure out how the bullets will behave. This time, there are two velocities to take into account. The raptor is running up, and the bullets are flying to the right. So in the view of the raptor, the bullets have a velocity that is down-and-to-the-right. Note that we are being extremely qualitative. Velocity addition in SR is more nuanced than in the standard Newtonian world, but all we care about is that the bullets seem (to the raptor) to be going down and to the right. For ease of our picture, imagine that we’ve chosen the velocities such that the final summed velocity points from one corner of the dotted-line-rectangle to the other.

Then we squish the bullets’ frame along its direction of motion. So in our example, we squish from one corner to the other. (That dotted rectangle around the bullets just helps us keep track of how the frame contracts. You can even pretend it is real, if you’d like… its addition doesn’t affect the results, just makes the picture clearer.)

Again, just a simple Length Contraction. Nothing special. So why did I pretend this was strange?

Ah yes, the final step. Let’s put all the pieces together. The raptor, room, and bullets of course exist together.


And there you have our result. The room is squished in one direction, the bullets in another, and thus the bullets are no longer sitting on a horizontal path across the screen. The cannon (where we know the bullets are starting) and the target (where we know the bullets are ending) lie along a perfectly horizontal line. But the bullets do not. They are sitting on a path aimed up and to the right. At an angle. So you won’t always find the bullets (seemingly) directly between the cannon and the target. In fact, depending on where the raptor stands, she may even see the bullets as emerging at a point distinct from the cannon… and disappearing at a point distinct from the target.

But remember, we didn’t do anything special. No magic, no tricks. Just boring old Length Contraction.

We have, in fact, rediscovered a known fact with our pictures. Two Lorentz boosts in non-parallel directions (aka combining the raptor’s motion and the bullets’ motion) together make not just another Lorentz boost, but also a rotation. Hence why the bullets don’t just seem squished, but also rotated.

Counterintuitive? Sure! But what good result in physics isn’t?

*Did you find a mistake in the steps? I’d love to hear about it. After all, in science, we must always reserve the right to be wrong 😉


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Updated Velocity Raptor

Posted in: Velocity Raptor | January 30, 2012 | No Comments

A couple changes to Velocity Raptor:

1. A few minor bug-fixes
2. Revamped art

I’m hoping a bit more polish to the graphics will make the game a better experience for the players. Check it out, and see if you agree!



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Velocity Raptor Released!

Posted in: Velocity Raptor | December 15, 2011 | No Comments

Special Relativity. And dinosaurs. Could you ask for more? Go play this fun flash game, and master all that abstract physics in the process.

As one player (unprovoked) said: “I learned more playing this game for 15 seconds than I did in a semester of physics class.” Who am I to disagree?

And lest you think this is all just idle fun, this is a true Special Relativity simulator. Developed from the ground-up, it presents a 2D view of a world where light is slow and you move fast. The warping you see, the strange color changes, and the odd timing-effects are NOT approximations. They are not ‘artistic renderings’ of what you’d expect to see. This is truly simulating a world according to the rules outlined by Einstein. Painstakingly crafted for your gaming pleasure.



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