In Probability 0, the goal is to go down while the platforms rise and all sorts of baddies try to get at you.

This vertically scrolling, procedurally generated platformer comes from TIGForums member Droqen, and it recently passed version 1.0, then quickly rose to version 1.05. And more things are to come, but the game is more complete than not, so lets review.

Gameplay

The idea behind the name is that instead of a health bar, you have a number that represents the current probability of your survival. It starts high, shifting between four- and five-digit numbers, then falls as you take damage, venture too close to the top or bottom edge of the screen or generally creep too close to danger. Should it drop to zero, it’s game over.

Though only damage can push you to that number, there are plenty of ways to take a hit. If you fall to hard, if you touch a spike, if you touch one of the creatures or if one of their projectiles catches you, you take some damage. The purposefully obscure health bar makes it hard to tell how much damage you’ve taken, but it only takes a few to die.

The game is hard, not because the platforming is particularly cruel or the monsters particularly nasty, but because you start with few ways to defend yourself. The character can only punch a very short distance and throw ninja stars straight down. As you progress and level up, you can build up your character’s talents, and eventually become pretty powerful. Though I eventually became pretty proficient with the stars, I rarely used the punch, because you have to be right next to something to hit it, and nearly all the enemies float.

You do have the option of starting the game with four upgrades, but by going that route, you forgo any further improvements. Since there are 20 abilities to gather, limiting yourself to four doesn’t seem like a good idea. But going that route is the closest thing the game has to a tutorial, and it’s a good way to test the early abilities.

And the abilities do all sorts of neat stuff. They increase your ninja star stores, allow you to fall further before taking damage, punch through the previously unbreakable black blocks and even shoot through walls. You gather abilities by leveling up, and the only way to do that is to pick up the floating balls left by dispatched enemies.

Each time you pick up one of the balls, you get the next item in the pick-up queue. You know at all times what the next three items are going to be, a mix of hearts, stars and up arrows. Hearts repair damage taken, stars fill your ninja star pouch and the up arrow grants the next level. This queue gives some predictability to an otherwise random game.

As you descend, picking up levels and growing more powerful, you’ll come across the four mini-bosses. They spawn randomly and tend to have more health than the other creatures on the screen. You aren’t required to beat them, but they’re usually hard to avoid, and what they drop is valuable enough to make an engagement worthwhile. Eventually they spawn in twos and threes, making things a bit more hectic. There is no bottom to the pit; you just survive as long as you can, aiming for the high score.

Story

Nothing much to report here. The only thing you know while playing the game is that going down is good and touching anything with red eyes is bad. I’d like to know something more about what the character is doing and why the creatures are so mean to me. Even something as simple as a bestiary would be nice.

Style

Almost everything is black against a dark, blueish purple background. I know that sounds like it would be hard to see what’s going on, but it’s surprisingly easy to follow what’s going on. The few bits of red and white separate the good from the bad. Your eyes are white, as are the pick-ups and the ninja stars. Anything red is dangerous. The red spikes are obviously bad news, but the invisible creature’s red eye can tip you off to its location.

The art is blocky and competently animated, though with every living thing being black, there isn’t a whole lot of differentiation between creatures. The music is pretty repetitive, based around four notes that drone on and on. But it changes depending on how well you’re doing. If you’re about to die, subtle alarms go off to let you know you’re in trouble.

I really like the menu. It’s turned 90 degrees, and it grabbed my attention the first time the game started up.

Everything Else

Like Spelunky — another hard, procedurally generated platformer — the time between your first play of Probability 0, and the first time you reach the end will be lengthy. But the feeling of accomplishment that comes as descend further and further feels pretty good.

[Download the game here]