This blog post contains extensive spoilers about a new mob in the adventure update. Don’t read unless you want spoilers!
Fear is one of the easiest emotions to evoke, but doing so in a way that doesn't frustrate or fatigue the player is more difficult. I find this fascinating. What parts of fear are fun, and what parts aren't fun?
One of the biggest game design decisions in Minecraft is that all (well, most) negative things that affect the world or the player should happen near the player, and be clear to the player. That's why creepers only explode near players, and that's why fires stopped spreading indefinitely. This is somewhat related to my dislike of mazes in game design, where the player has no way of knowing or figuring out before hand what decision is the correct decision. Don't penalize the player for things they can't control.
Last weekend, I started working on a new mob because I was frustrated with the slow progress on some town code I was writing, and for some reason I decided to make yet another creepy one. It's dark, it has long and narrow limbs, moves very slowly, and will pick up blocks and move them around. I wanted this to be a mob you only saw in the distance and a mob you'd be afraid of, but when I playtested it, it mostly felt like a regular zombie. There's was a distinct mismatch between looking creepy and not actually playing creepy. When I made it move faster towards the player when attacking, and deal more damage, it got more difficult and I started respecting it, but it never felt creepy or scary.
So I thought some about what “creepy” actually is, and it's more about trying to avoid something from happening than it is about actually having that thing happen. If you know something bad can happen if you do the wrong thing, you will start thinking about your actions, and that might make things more scary.
So I made it passive until you looked straight at it. And that was scary. Suddenly you could walk up to these looking beasts (they're three meters tall) and watch them as they moved their blocks around, but as soon as you happened to look straight at them, they'd attack. And by “straight at them”, I mean putting the reticle on top of them. You can keep them visible on screen and actually look straight at them in real life, but as soon as your in game character looks straight at them, boom.
Still, that was more scary than creepy. It's like a jump scare in a movie. You know it might happen at any time, and when it happens you freak out a bit. I wanted something a bit more psychological. So to really drive home the point of looking at them being bad, I made the Endermen freeze and turn towards you when you look at them. As long as you look straight at them, they stand perfectly still and look straight at you. As soon as you look away, they will run (very fast) towards you.
And they teleport. If they're too far away to reach you in a short period of time, they will teleport about once per second. They try to make sure they always teleport to somewhere you can see, as I don't want to confuse the player as to what is happening.
When they attack, you know it's your fault. When you happen to look at one, you can keep looking at it to figure out how to deal with it, but you know it WILL reach you very fast once you stop looking at it.
And that, my friends, is creepy. Possibly too creepy.