You have already lost. Before you play the game. Before you consider playing it. Before you’ve even read this review, you have lost. You will be cast into a black abyss filled with monsters, and you will die. You may learn, you may become stronger and you may feel some inkling of achievement along the way, but you’ve lost anyway. As far as I’m aware, there is no victory to be found here, but I’ll keep trying anyway.

Originally a freeware game (which you can play here), the expanded, upgraded commercial version of Probability 0 by Droqen is a survival platformer with some roguelike elements, and an air of inescapable fatalism that you won’t find in many other games. Taking place in a single, narrow screen, you descend deeper and deeper into an auto-scrolling pit full of spikes, monsters, destructible blocks of various varieties and inevitable defeat. At the start of any given playthrough, all you can do is jump, punch, and throw a limited stock of star-shaped projectiles directly downwards, and only when jumping. Through defeating monsters, you gain experience, and with each level gained, you get to choose a new ability from a slowly expanding skill-tree.

Every decision is vital, and how you develop your character is very much up to personal preference. Do you want the ability to punch through solid blocks? Stronger knees to survive longer falls without damage? A sideways or upwards projectile attack? The power to bounce on heads to do damage and break falls? Each choice changes the way you play, and given the semi-random order at which each playthrough introduces new enemy types, you might find yourself adapting to deal with threats as they appear. Each time you play, you – personally – will learn how to handle things a little better, and what skills suit your style. Each new enemy encountered gives you a new gameplay element to learn and counter, and each new skill must be mastered. It’s a simple game, but with impressive depth.

If you’re easily frustrated, then this game isn’t for you. If the idea of each new threat being hidden just out of sight sounds unfair, then you won’t like this either. Probability 0 isn’t a game for everyone. There’s not a massive amount of content, and only a couple of additional playmodes (a higher difficulty mode, and ‘Karma’ mode, where you shoot for a high score with a fixed character level), so some might not think that the game is worth the full asking price.

Still, this is one of those games that sets out to achieve one thing, and does it so well that you might not care that it isn’t the most fleshed-out of packages. I’ve gladly sunk a few hours into the game already, and will likely play it more after this review. There are depths I’ve not yet plumbed, creatures I’ve not yet fought, and skills that I’ve yet to try. It’s compelling, addictive stuff – more focused and refined than Spelunky, or almost any roguelike.

All of this is held together by a singular, focused aesthetic. You can see it all in the gameplay trailer above. A stark, clear, silhouetted world. Sparing use of colour, with white focuses on powerups and your character to catch your eye, and red highlights on anything hazardous to your health, and a multi-layered but single-track musical accompaniment that fades elements in and out as you play. It’s a great composition, and while it has energy and drive behind it, there’s a definite funereal, elegiac note to it. A fitting piece, given your inescapable demise. And, of course, the ever-shifting number. A flickering reminder of dwindling hopes. Each time you make a mistake or take a hit, the number shrinks. It’s memorable, effective stuff.

You can buy Probability 0 direct from the developer for $5 (discounted until November), or for $10 in a bundle with three of his earlier games.