a series of interesting choices thoughts on game design from paul sottosanti

the shields system of bit pilot

The goal of Bit Pilot is to stay alive as long as you can. Well, scratch that. The goal is to listen to as much of the music of Sabrepulse (an incredible chiptune artist) as possible, and the way you do that is by living as long as you can. You control a little ship in a huge asteroid field, with your only input being surprisingly tight touch-based movement controls. There are two powerups that occasionally float onscreen; a score powerup that grants 1000 points, and a shield powerup that grants 250 points and adds a hexagonal shield surrounding the outside of your ship. Each shield will block one asteroid that otherwise might kill you, but there's a catch: each one also makes your ship significantly larger. With no shields, you can nimbly slip through the tiniest cracks, but you're also instantly dead to any laser or asteroid that makes contact. As with all games of this ilk, death equals starting over from the beginning.

Recently I tweeted: "Bit Pilot's shields system is one of the best and most elegant examples of dynamic difficulty I've seen. Simple but brilliant."

Greg Marques requested that I go into more detail, and seeing as it was just recently his birthday, who am I to turn him down. Here's why I made that claim:

It keeps the game interesting for players of all skill levels. The basic goal of any dynamic difficulty system is to provide a suitable challenge without forcing players to self evaluate their skill level. (Since players tend to be fairly bad at the self evaluation, especially without enough context, and also are often incentivized to choose something far too easy in order to achieve unlocks or higher scores.) The system works admirably in this respect, as a strong player can build up a huge stockpile of shields, making it difficult to weave in between even the smallest asteroids.

The difficulty increase is visual and directly player driven. A common problem with dynamic difficulty systems is that they're hard for players to comprehend. Once a player knows that something is going on behind the scenes but doesn't understand it, it's easy to feel cheated and blame the dynamic difficulty system for providing artificial challenge. In this case, though, it's easily understood because it's carried out in a visual way directly at the point of the player's greatest focus, the ship.

It works towards solving a common problem with the genre where the early game is boring for strong players. I have a hard time playing any of these "survive as long as you can" (Canabalt, RunRunDash!, Monster Dash) games for long because the game experience gets worse the more skilled the player becomes. Not only does each individual game start to take longer, but there's also a steadily growing period of boredom at the beginning as you wait for the difficulty to ramp up. While the shields system doesn't completely solve this problem, it does mitigate it greatly, as you can now spend the early game trying to build up a reserve of shields to get you through the harder later stages, and manuevering with those shields is tricky.

It turns getting hit from a negative experience into almost a positive one. This is a subtle effect that I think is actually quite important. Typically in these sorts of games, getting hit (or falling off a building, or whatever) is a strictly negative experience. There's nothing wrong with that, and in fact the whole game is built around avoiding it. In Bit Pilot, though, the fact that your ship suddenly becomes smaller changes the feeling completely without doing something drastic like removing challenge or consequence. So many times I've gotten hit and found myself thinking, "Sweet, I'm smaller now!". Most of these games have an arc that just slowly builds linearly and then eventually plummets off a cliff when you make a mistake. Bit Pilot's is more like a traditional roller coaster, with a steep initial climb and then numerous peaks and valleys.

There's no question whether or not the shields are worth it. Another common problem with dynamic difficulty systems is that they will drastically warp player behavior. Oblivion is a famous example, with players intentionally staying low level while training critical skills and trivializing much of the gameplay. However, in Bit Pilot the shield powerups are obviously worth picking up, since an extra life is always worth having no matter how difficult the gameplay becomes (assuming it drops back down to the old difficulty when you lose the life, which in this case it does). I haven't found the system changing my behavior in negative ways at all.

So there you have it. An incredibly simple design choice (each shield makes you bigger) with far reaching positive effects for the game. If you get a chance, try out the game and let me know if you agree or disagree.