Never reach the bottom of the pit that is Probability 0. The game is different every time you die: the enemies you fight, the landscape you climb down, and the body you inhabit (if you so choose). Never survive. But find your way deeper than you did last time.
User reviews:
Mostly Positive (48 reviews) - 79% of the 48 user reviews for this game are positive.
Release Date: Oct 1, 2012

Sign in to add this item to your wishlist, follow it, or mark it as not interested

Buy Probability 0



“... more focused and refined than Spelunky, or almost any roguelike.”
The Indie Game Magazine

“Probability 0 is a different kind of arcade game, one that will challenge your brain as much as your hands. Come for the endless downward action, stay for the cool upgrades you can bestow upon your character.”

About This Game

Probability 0 is a downward-scrolling infinite arcade platformer.
There are a million ways to fight for survival.

Descend: as you combat the darkness, improve yourself. Build yourself up as a star-thrower or a teleporting menace. Learn to traverse the pit's many dangers, from threatening monsters to unforgiving gravity. Walk across spikes that once frightened you. Punch through walls that would have doomed you. You'll never be invincible.

Descend: enemies grow more numerous. They will destroy the floors beneath your feet, spit death at you, and cannibalize and infect each other in their mad swarming. Your foes will be invisible, or reckless, or explosive, or seemingly untouchable. Deeper dangers will always find a way.

Descend: and die, as you did last time and as you will next time. But find your way deeper.

There are a million ways to fight for survival. There is no way to survive.


Let's talk like people, now, and not like the back of a videogame box.

I designed Probability 0 years ago, and released its first version for free in late 2009. Back then, it embraced a randomly-generated landscape (so I wouldn't get bored of it), introduced higher-order enemies to the spawn queue in a random order (so I wouldn't get bored of them), and allowed you to buy upgrades from a vast and unrestrictive talent tree (so I wouldn't get bored of those). Oh, and death wipes everything (so I wouldn't just get everything... and then get bored of playing & replaying the whole thing).

On top of that, the enemies and powers are designed to be significantly different from one another. There's an enemy who literally eats other enemies and spits their digested corpses at you. (Mechanically speaking, their 'digested corpses' are always the same handful of red globs -- but what fun is it, thinking like that?) There are more mundane enemies, of course, but one who moves in random, erratic angles is very different to fight than one who always moves straight towards you.

The set of powers, on the other hand, were made to offer you a lot of choices. There are ~36 of them and contain nearly zero arbitrary prerequisites. Buy the powers you want to have, not the boring ones you'll need for the future. Every time you level up, a new row opens up and you can buy anything from any row except for abilities that build on a lesser version of itself -- you can't get the 'never take fall damage' powerup without first having the 'take less fall damage' one. There are also none that don't augment your choices in an interesting way. You're not choosing between +10% armour and +10% damage; who cares, when you could instead be choosing between immunity to every spike in the game and upgrading your punch to kill any enemy in one hit? Those aren't even top-tier powers.

I'm still not bored of this game, and remember that it started in 2009. There are boss enemies who appear intermittently, to shake things up. There are enough abilities to try thousands of different builds, if you're feeling a little stale. There are enemies who don't even appear until you've gone deeper than I can most of the time. You'll probably die before seeing any of these things, but don't let that stop you. Keep dying.


Don't forget about JMickle's dynamic music. Its layers fluctuate as you dive deeper: the bass comes and goes; the chords swell and die; and the sirens scream as death approaches. You can hear it in the trailer, in the game itself, and even more below -- click on the soundtrack in blue and the remix album in magenta.

System Requirements

Mac OS X
    • Memory: 1 GB RAM
    • Storage: 20 MB available space
    • Memory: 2 GB RAM
    • Storage: 20 MB available space
    • Memory: 1 GB RAM
    • Storage: 30 MB available space
    • Memory: 2 GB RAM
    • Storage: 30 MB available space
Customer reviews
Customer Review system updated Sept. 2016! Learn more
Mostly Positive (48 reviews)
Review Type

Purchase Type


Display As:

(what is this?)
40 reviews match the filters above ( Positive)
Most Helpful Reviews  Overall
48 of 61 people (79%) found this review helpful
6.9 hrs on record
Posted: June 13, 2014
The simple action of a platformer with a touch of roguelike complexity. From the mind behind Starseed Pilgrim, Probability 0 takes the straight-forward yet challenging run n' jump gameplay of platformers like VVVVVV and stirs the formula up by applying the dynamically randomized levels, skills, and enemies of the roguelite genre (Spelunky, Risk of Rain) for an end result that is infinitely replayable and impossible to master.

The challenge in P0 is refreshing, while a lot of your runs will quickly end in your swift and humiliating failure the few runs you do make it far on will feel that much more rewarding and satisfying. There are loads of powerups to play around with all located on a large and expansive skill tree that you are able to upgrade between each level you manage to surpass. Every choice will have a huge impact on how you play and every player will find their own unique path of skills on the tree to succeed by.

The game has a simple but abstract and almost horror look with a great atmosphere. There's a large variety of creepy creature designs, dark and moody colors, and a rapidly changing Probability message scrawled at the top of your screen to remind you of your impending doom. The soundtrack alines perfectly and feels dark and ominous for something so 8-bit and catchy, fitting with the mood of the game just right.

At less than ten dollars, Probability 0 is an easy buy for all fans of platforming and random roguelike elements and will be remembered by me along with the most famous of indie titles from this era.
Was this review helpful? Yes No Funny
13 of 15 people (87%) found this review helpful
1.7 hrs on record
Posted: June 13, 2014
Probability 0 is an elegantly designed little roguelike platformer. It puts you in the shoes of an unnamed dungeon delver who has absolutely no chance of surviving the adventure, as you might have surmised from the game's title. Instead, the focus of the game is simply to delay your inevitable death for as long as possible.

There's no traditional life bar, but you can roughly tell how much health you have left by two things. One is the "probability number" near the middle of the screen, which constantly fluctuates between various encouraging statistics such as the "chance in a million that you will ever see your family again". The second way to tell how close you are to death is that the music becomes increasingly intense, and a siren can be heard in the distance. Is it the song of the valkyrie coming to take you to Valhalla, perhaps, or the grating sound of Hell's gates swinging wide in front of you? The same siren can be heard when a boss monster appears. Coincidentally, that is also the moment where you are most likely to die.

With its branching skill tree and randomized levels, the game has much replay value. Thankfully so, because each run through the game is extremely short. Progress is measured in minutes rather than hours, and a newbie might simply perish by falling off the platform they started on. You may begin to feel burned out after dying many times in a row, so I think this game is best suited for coffee breaks, or as a filler played in between other activities. What I find most enjoyable is to simply play two or three runs each session, and then stop for a while to let the lessons learned from those runs sink into my mind.

In short: If you're looking for a platformer that challenges you without wasting your time, Probability 0 is an excellent choice. It generally takes only a few minutes for your character to die, but it leaves you with the feeling of wanting to try again and to do better next time. To exact vengeance upon your killer. To see your family again... well, the probability of that happening is zero, but it's worth trying.
Was this review helpful? Yes No Funny
10 of 11 people (91%) found this review helpful
21.5 hrs on record
Posted: October 27, 2014
This Game is the One of the Most Polished, and AWESOME Games I've ever Played.

Makes me Wonder why this Game isn't on the Featured Items Page...

I have to warn you though: This is Pretty Hardcore. Even Beginner Mode is tough.
And Expert...Yikes.

The game, like the store page says: Involves the Player to traverse increasingly difficult depths
stuffed full of Monsters who want you DEAD.
Everytime you kill a Monster: you can grab it's 'bubble' which gets you to level up.
When you level up, there are really cool upgrade trees that are instantaneously put into play.
And you start from scratch every time you die.
And you Die every time, as this game doesn't have an end.
So the Replay value of this game seems practically Infinite.

And That's Only the Beginner and Expert Modes!
There is also the Karma Mode which let's you instantly get a limited number of upgrades to start with.
But that's all you get.
Then you are thrown into a Horde of enemies.
Have Fun.
Note: Karma Mode Levels('Karma XX') build up as you play the Beginner and Expert Modes.
Note 2:When you Start the Game, it may throw you STRAIGHT into Karma Mode. And Use a Level, so don't start opening and closing the Program unless you need to.
If you aren't in to fast paced platforming where you WILL die. Then don't buy it. (But Please give it a try anyway.)
But else, BUY IT.

Don't be Discouraged that this game doesn't run on Linux though, It runs PERFECTLY on Wine(Wine Is Not an Emulator, which is a Open Source Compatability Layer that trys to get Windows Programs to Run on Linux; it isn't perfect, but it's still great.)

I think personally that Valve should team up with the Wine Development Team to Help make Wine better and get more steam games to run on Linux without requiring developers to rewrite/port their games to Linux.

My Suggestions for the Game are:
--Add a Local Multiplayer Mode: It would be Really Fun to have Either a Co-Op/Competitive Mode where 2 or more players would be trying to share the resources/trying to kill each other while simultaneously dealing with the
terrain and enemies!
--Make an infinite mode: This one is optional, but I would like to have a 'God-Mode' where I could play around and see what it would be like to have ALL THE ABILITIES AT ONCE! :)

I Definitly Recommend this Game!!!
Was this review helpful? Yes No Funny
12 of 16 people (75%) found this review helpful
3.4 hrs on record
Posted: June 18, 2014
If you're into your roguelike-likes (you know, games like Spelunky and Binding of Isaac), Probability 0 is a must-play. You venture downwards, killing enemies to progress and collecting powers that help you beat the more difficult baddies down in the nether regions. Ironically there's a huge amount of depth to this game, and much like with Spelunky, it's only after several hours (and dozens of deaths) that you truly begin to see its full worth. You can watch my playthrough here:
Was this review helpful? Yes No Funny
5 of 5 people (100%) found this review helpful
6.4 hrs on record
Posted: June 20, 2014
10/10 would die again.

Probability 0 is the basic concept behind roguelikes boiled down to a very few key aspects, and mixed with some clever design elements. It's pure, accessible, deep, and has an eerie, mysterious vibe to it. The platforming and combat both start out really simple, and are continuously expanded upon through new abilities (like firing your ranged projectile in new directions, being able to stomp your enemies, smash otherwise solid blocks, just to name a few). It's worth mentioning that the skill tree is extremely refined and well-designed. It feels balanced, interesting, and allows for an astounding amount of customization and experimentation at the same time.

Enemies start off really simple, but as you get deeper, the spawn pool gets mixed up with very interesting critters that drastically differ in their movement, attack pattern and other behaviour. Since each enemy and environmental hazard is extremely easy to grasp and learn, death is rather caused by multiple of these elements driving you into situations you didn't calculate. Each death, even if they are very frequent, feels more than deserved - an aspect lacking in quite a number of other games.

I would definitely recommend Probability 0 to everyone who likes a good challenge. It can be frustrating, but in the most positive way a game can be. It's pure in its design, fun to play and very rewarding.

Was this review helpful? Yes No Funny
4 of 4 people (100%) found this review helpful
11.4 hrs on record
Posted: June 23, 2014
I picked this up on Steam a few days ago and have become slightly obsessed with it. as in, I am hearing the music in my dreams at times, and find myself humming it as I go about my day.

it's a lovely, quite melancholy trip into the abyss, in which a hapless fellow bounces about, shooting stars and trying not to run out of probability.

I'll explain that last, later.

there are three game modes --

in Beginner, the object is to scatter as many foes as possible. in short, kill them without mercy.

in Expert, it's depth that matters -- delve as deeply as possible before your chances run out.
oh, and you should probably still kill things, so you can level up... but the depth's the real thing here.

I'll get to the third mode in a moment, because a bit of explanation must come first.

when you destroy enemies in either Beginner or Expert, an experience orb appears.
sometimes it's JUST experience. sometimes it comes with 3 or 6 shots of your star.
sometimes there's a little heart inside, which does just what one would expect -- it boosts longevity a bit.

getting enough experience grants a level-up, which appears as a brightly-flashing line across the playfield. crossing the line lets the character gain a new ability (or improve an existing one),
as well as cancelling any fall and healing the same as though one had picked up a heart.)

in this game, the health meter is insane.

there's a rapidly-changing set of phrases and numbers in top-center, all expressing probability of some desired outcome.
when a run begins, these numbers are in the 5-6 digit range mostly, but as your fellow takes damage, the numbers dwindle -- when you see 1-3 digits and hear the warning siren coming into the music, it's time to be super careful.

that same siren also sounds, much more loudly, whenever a particularly dangerous enemy boss shows up.

eventually, luck runs out, and one's left staring at a big fat 0 under some statement of what could have been... but won't be, no matter how much you play.

death is inevitable here, but it can be really fun getting there.

finally, I'll mention the third mode -- Karma -- which is what makes P0 even more awesome.

playing Beginner and Expert runs gives Karma credit.

Karma maxes out as 10 ("X", in game terms). when playing a Karma run, you get to select as many abilities as the number of Karma levels allows, and go through an even-harder-than-expert run to prove your mettle. (you also lose 1 level of Karma each time you do a Karma run, but it's not terribly hard to regain the level by playing Beginner/Expert a few times.)

in this mode, collecting the orbs enemies leave after death is the object -- which makes it the most difficult thing, especially since Karma mode teems with enemies who can easily get in the way of scoring the spoils of recent kills.

in short, it's very replayable and lots of fun. my only real regret is that it doesn't have more variety of music, but that's not such a big deal, as the music that it DOES have totally fits the action.
Was this review helpful? Yes No Funny
4 of 4 people (100%) found this review helpful
1.4 hrs on record
Posted: September 9, 2014
There is no point to this game but the challenge. No achievements, no online, multiplayer, co-op, or leaderboards. No saves. Nothing to unlock. No steam cards. None of that.
What yu DO get is two difficulties, Beginner and Expert. Beginner is hard enough. You get your own personal high score. Not scoreboard, just score. Then you get one other mode called Karma, where you get to test your skills with preloaded abilities, but no leveling up at all. If you ever played Fall Down on the TI83/83+/84+ calculator, it's a bit like a twisted version of that.
Don't get me wrong, this is not an awful game, but it is a matter of preference. There is no incentive to playing this game other than your own satisfaction in the challenge and testing your skills.
Was this review helpful? Yes No Funny
5 of 6 people (83%) found this review helpful
1 person found this review funny
8.4 hrs on record
Posted: October 6, 2014
Severely underrated, bombastic music and endless replayability. KNEES SHOULD BE A PASSIVE NOT AN UPGRADE THOUGH SERIOUSLY GUYS THE FALL DAMAGE HURTS SO BAD.
Was this review helpful? Yes No Funny
5 of 6 people (83%) found this review helpful
0.5 hrs on record
Posted: February 27
I was unaware that Downwell had any competition in the "low-res roguelike platform descent" genre until my friend put me onto Probability 0. There's less of a setup and more of a high-concept motif here, with your silhouetted pixel man descending into a never-ending pit of darkness, battling strange monsters along the way. You start out only punching and slinging stars downward, but defeating enemies levels you up and allows you to select from dozens of new abilities across several tiers. There's space for some actual builds here, such as ones heavy on punching, or stars, or defense, or contact damage, and so on.

Despite the advancement options, there's not much variety of gameplay to use them on. You'll encounter more and stranger monsters the further down you go but the basic structure of the pit doesn't change from assortments of blocks and spikes. It's not necessarily a bad thing, it just strays closer to an infinite runner than, well, Downwell. The fixed scrolling also means your pace is mostly dictated by the game, making Probability 0 feel the more measured and technical of the two.

The title refers to the game's most unique aspect, the probabilities that constantly flash across the upper center of the screen. This is essentially your health, as the random probabilities decrease as you get hit, from six digits all the way down to singles. It's a clever touch that really supports the surreal, striking feel of the game you get from the stark graphics and steady, low-fi soundtrack. There's two difficulties to tackle plus a mode where you can get a head-start based on your previous records, but again, not a lot of variety between runs aside from your builds. As long as you're okay with that, though, there's a pretty good chance you'll enjoy this one.
Was this review helpful? Yes No Funny
6 of 8 people (75%) found this review helpful
Not Recommended
0.9 hrs on record
Posted: December 16, 2014
It's not a bad game by any means, it just gets very repetitive.

The upgrades are fixed and you'll generally find yourself sticking with one set upgrade path each run because it's the only one that ever really works. The enemies move randomly and are very difficult to hit, and since the progression - at least of Beginner Mode - is done by how many enemies defeated it makes the game pretty frustrating. Also, the controls are fiddly, meaning you'll slip off platforms, walk into enemies and generally not do what you want to do. Also also, there's fall damage and a lot of the time it's unavoidable.

Altogether it plays more like a budget flash game. Try it if you've got some spare change and it's on sale.
Was this review helpful? Yes No Funny
Recently Posted
I Wanna Be The Grand Master Dev
0.3 hrs
Posted: September 10
Pros: Good soundtrack and challenge, pretty fun.
Cons: HP-meter has crippling depression.
Helpful? Yes No Funny
0.2 hrs
Posted: December 23, 2015
It's certainly not anywhere near the worst game I've played. It's just that the combat, which is sort of essential to the gameplay, feels really bad. I realize the entire point of the game is to get further by upgrading, but you start off so terribly weak and frail that it's hard to really make any progress.

I think some people will probably love this game, but I personally cannot recommend it.
Helpful? Yes No Funny
fumped garlic
0.2 hrs
Posted: November 29, 2015
Helpful? Yes No Funny
2.2 hrs
Posted: September 26, 2015
Probability 0 is a procedurally-generated infinite platforming game with roguelike elements. The only real goal of the game is to survive as long as possible as the game automatically scrolls downwards. You build up a score based on the number of monsters you defeat while descending, and you level up with the experience points that the monsters drop. Leveling up gives you new skills that will increase your chances of survival, but the odds are always stacked against you. In fact, there's 0% chance you'll beat the game.

The gameplay is very simple, but tough to master. At the start, your combat abilities are shooting stars beneath you while airborne and punching. Both are pretty weak, but as you gain new skills, you'll become more formidable. There's a wide variety of monsters to face, each with unique patterns and abilities. Touching them knocks you around unpredictably, exposing you to other dangers below. If you get far enough, you'll even face tough boss enemies! The game's challenge is always in a constant state of pressure: you have to avoid getting crushed by the scrolling ceiling above while taking care not to fall into the abyss without a platform.

The game's real charm comes from its aesthetic. It features simple pixel graphics with a soundtrack that pulses and screams as you get closer to death. Your chances of success are constantly shown on the screen instead of a health counter, while the distance you've traveled is recorded in all sorts of different units. Everything is incredibly cute, which fits Droqen's style from past games, like Starseed Pilgrim.

Unfortunately, Probability 0 still has its fair share of problems. There's no native controller support, and the dev doesn't seem to be responsive to players on Steam's forums. Droqen has seemed to have moved on to other projects and isn't interested in offering support. The game's engine was done in Flash, which isn't particularly favored by many players. Personally, it lags a bit for me. Some may find the game's unconventional systems to be a turn off: there's no HP display other than your odds, and the habit of monsters knocking you around is pretty frustrating. Finally, a lot of people will probably find the price to be quite steep for what it is. I'm not sure what to say to really justify its price other than that it was a true labor of love by a humble indie game developer and that it's a pretty fun score-chaser.

TL; DR: For fans of Downwell, TowerClimb, Just Get Through, Spelunky, and other roguelike platformers.
Helpful? Yes No Funny
73.3 hrs
Posted: July 6, 2015
The gameplay is straightforward, so I'm skipping to the nitty-gritty. You saw the trailer.

Balance in single player games is something I've come to value more and more over time. I've seen too many games where one weapon or upgrade is simply the best, not even a matter of preference, and choosing anything else is tantamount to shooting yourself in the foot. Using the best option feels awful, and using a worse option on purpose feels like I'm putting in more work for worse results. I was worried that this would be one of those because I immediately said "THIS skill is the obvious choice", but if an upgrade seems like an obvious choice do yourself a favor and try the other ones too. Every single upgrade rocks the foundation of the game in a good way. The best games make every option feel like a game-breaker, but keep everything balanced. The lower tier skills are often just as tempting as the higher ones. This sounds like a small thing, but it's so satisfying to pick a useless skill and see it's great, or skip a absolutely necessary skill and see it isn't.

The platforming seems simple, but small details make it deep. The jump height, block size, and overall physics of the game are calibrated to give you as many choices as possible. This part is difficult to explain, but since the game is made of blocks in a grid pattern, block configurations can reoccur. The hang time on the jump is such that you can JUST clear a two-block gap with a ceiling overhead. The ceiling prevents you from getting the height you usually need to get across, making it difficult. But since it's a grid layout any time you see blocks arranged that way, it's the same exact jump, allowing practice to carry over. The punch hit-box is just enough that if you stand on the VERY edge of a block you can hit a block one block away. The grid size is just enough that you can jump off the edge of a block without bumping into the one directly overhead. Things like that. Little maneuvers that are tricky, practicable, and help you last a little longer if pulled off. If the physics were a tiny bit different, lots of maneuvers would go from "It's possible, but tricky" to "It's impossible", limiting your choices as a player.

Aside from the skill descriptions, very little is explained. I didn't expect much, but there was and still is a ton to discover. Several times I thought I had seen every enemy type, only to find another. Every skill has some additional detail purposely not mentioned in the description. Curiosity is really a one time feeling, but even after all this time there are still things I want to know. Is there something hiding down the Expert pit? Is there an ending? Is THAT bug actually intentional?

An unassuming, 12 MB, app-like game, but one of the most engaging I've seen.
Helpful? Yes No Funny
maximum smug
8.6 hrs
Posted: April 30, 2015
Beautiful little rogue-like platformer.

It begins with a simplistic concept that as you get to the lower levels, unlock upgrades that change the nature of the game completely. The first few upgrade tiers seem trivial, then quickly turn more complex and powerful reaching the higher ones. You can craft quite a few builds, whether you're going for versitile or just plain tanky.

Buy it.
Helpful? Yes No Funny
Enkazadas, Lord Of The Isles
1.6 hrs
Posted: February 17, 2015
It's not my kinda game, but it's a good game
Helpful? Yes No Funny
0.4 hrs
Posted: January 31, 2015
Maybe I'm just no fun, but I don't enjoy this at all. In mid-air you can only attack downwards? On the ground you have super-limited attack range? You actually do have to kill stuff to reach higher levels? I just don't see the point of this game, mostly, and for how cheap I got it I don't feel like dumping more time into it. Tried it a while back, didn't like it, tried it again today, didn't like it. So... oh well.
Helpful? Yes No Funny
Sprite Guard
54.0 hrs
Posted: January 29, 2015
I have a particular soft-spot for endurance-based high score games. I enjoy speed-run and time-attack games well enough, but for me there is a unique pleasure in trying to hold out for as long as possible. This is a particularly good example of the genre, and it captures much of the magic that was pioneered by classic examples like Donkey Kong. In Beginner and Expert modes, every game is a fresh start. This makes runs comparable -- no need to wonder "did I only do better because I unlocked something?" -- which is essential in a high score game. The unlockable "Karma" mode is very comparable as well, because there are only ten levels of unlocks, and you unlock them fairly quickly by playing the other two modes.

Some of the mechanics in this game feel downright un-fair. Your projectiles have a tiny hitbox, while you have a rather large one, so it's a common occurrence to throw a star straight down, miss, fall straight down after it, and be hit by the monster that your star had missed. Projectiles also travel downward a bit slower than you do, so it's possible to pass them on the way down. The distance required to trigger fall damage is quite small. Getting hit sends you into a stun animation that can launch you quite far, sometimes it will throw you helplessly to the bottom of the screen, which is instant death.

They seem unfair, but they are surmountable. Developing the level of precision and quick-thinking that this game demands has been incredibly satisfying. Much like Starseed Pilgrim, another game by the same developer, this game presents challenges that seem impossible, which makes it all the more rewarding when you finally figure out how to overcome them.

The main flaws are a lack of leaderboards and controller support. Joy2Key mostly overcomes the controller issue, but it is less convenient. The lack of leaderboards is disappointing, but it focuses the game on the learning process rather than the competition, and ultimately the learning process is where this game's greatest strengths lie.
Helpful? Yes No Funny