Graph all the things

analyzing all the things you forgot to wonder about

# Rogue Earth

2020-08-25
interests: little webgames

Use wasd or arrow keys to move, p to pause, n to reset/start a new game.

The brave people of Earth have equipped the whole planet with massive thrusters and entered a cage match with other planets. It was a decision that made sense at the time. See how long you can survive without colliding! Collect power ups to help your quest!

I originally made a game like this in late 2007. I found it intuitive and addictive, yet I've never seen another game with the same concept.

One interesting thought I had while recreating this: if object A has antigravity, it should repel B, but should B repel or attract A? The intuitive answer for me would be that B repels A as well, like two protons. But electric forces are based on the product of the charges of A and B, whereas gravitational forces (in Newtonian mechanics of course) are based on the product of masses. Since , negating A's mass actually negates the direction of A's acceleration as well, so the double-negation means that A is still attracted to B.

A physicist's take on the game:

• It can be solved if there is just one other planet; get into a stable orbit. Doing this appears to be very hard though.
• For more than 2 other planets, there is no stable equilibrium, so control will always be required.
• Kinetic energy is very bad, since particle speed increases the number of collisions per second. It also reduces your ability to react and move in time.
• Potential energy is good, as long as you don't end up releasing it. It means you're at a safe distance and nothing is accelerating too much.
• In general, adding more energy to this system is disadvantageous. It mostly ends up as kinetic energy. Energy is conserved, up to numerical error, except for your movement and the occasional antigravity power up. Through your struggle, it's almost inevitable that you'll gradually increase total energy and make your own survival harder.

#### Update: 2020-09-03

I changed the controls to apply equally whether you're trying to accelerate in a straight line or a diagonal. Previously you actually accelerated times faster if you were accelerating on a diagonal. I originally felt this made sense since the playing field is a square, and it would mean accelerating from rest in one corner to any of the other corners took equally long. But now I see that doesn't make much sense; gravitation works in its normal, radially-symmetric way, so why should the controls be different? Now accelerating in a straight line is 30% faster and along a diagonal is about 10% slower.