What is Surtension?
I made this game because I wanted somewhere to come back to every day, five minutes, the way you do the morning crossword — and because racing games bore me: going fast was never a decision in itself. So I turned the rule around. Here, speed is a currency. You earn it, you spend it, and sooner or later it sends you the bill. Everything else in the game follows from that.
In the browser, no account. A run lasts as long as you can hold it.
One control
Your finger, or your mouse, sets both the direction and the throttle: the further you push, the faster you go. There is nothing else to learn, no attack button.
The difficulty comes from one law of physics: your turning radius grows with the square of your speed. At a stroll you turn on the spot. Flat out, you need a quarter of the map to come about, and the dashed circle ahead of you — the tightest turn you have left — spills right off the screen. That is the moment you have to anticipate instead of correct.
What decides a collision
When two runners touch, it isn’t the faster one who wins: it’s whoever pushes hardest along the line of contact, as in a real impact. Someone overtaking you flat out in a straight line pushes almost nothing towards you. You, slower, ramming them broadside, put all your momentum into their flank.
Speed is the ammunition, the angle is the shot. The fastest runner on the map turns so wide they can no longer face what attacks them — nobody is untouchable, and that is my favourite thing about this rule. Every rival is coloured by how the collision would end right now: green, you take them; pink, they take you. The colour changes as you turn. That is the whole tutorial, and it never says a word.
Overload, and what it costs
Your gauge rises with your speed. The higher it goes, the more everything you take is worth, up to four and a half times. Above the red line two things change at once: the circuit can blow out and take three fifths of what you haven’t banked, and a lost collision destroys you — where below the line it “only” cost you half your charge and your momentum.
Dying here is not bad luck. It is something you chose by staying at the top of the gauge one second too long. I want that to stay true in every single run, and it is the thing I measure most.
Your charge isn’t yours yet
What you take from the others is not a score: you have to carry it back to the socket, the ring at the centre of the map. And you can’t plug in at full speed — you must give up your momentum, which is both your weapon and your armour, while carrying everything you’ve earned. Inside the ring nobody can touch you. It’s the journey home that is dangerous.
Every deposit raises your speed ceiling. You become faster, so deadlier, so a little wider through the turns. It is the only kind of wealth this game knows how to give, and it is paid for in handling.
The boost strip
The golden chevron strips push you above your own ceiling. That is not a gift: beyond the ceiling the gauge climbs faster than by any other means, so that is where you go to find overload — but coming off the strip you are a projectile that can no longer aim, and it is the angle that decides collisions. It hands you the force and takes away the aim, at the same time.
Take it when it’s in front of you; don’t chase it. I measured both ways of playing across a hundred days or so: folding it into your line is worth it, detouring after it is not. And you may simply decline — cross it slowly and it takes nothing.
Earning without killing
Grazing pays: skimming a barrier without touching it earns you charge, the more so the faster you go and the higher your gauge sits. Forty-six units closer, and it’s an impact. It is the path for people who prefer precision to brawling. It pays less than a takedown, on purpose: you should be able to live without fighting, not to win by avoiding it.
And one big deposit beats three small ones — up to twice as much per unit as shuttling half-empty. That is what makes “one more takedown before I go home” so tempting, and so dangerous, since everything you carry is lost if you fall.
Three grounds, one map a day
The date makes the map: every player on earth faces the same ground, the same traps, the same opponents, until midnight. There are three families of terrain, tuned so they don’t play alike: the circuit, a clean border and open ground inside; the maze, where you can no longer get around without lifting off the throttle; the plain, with almost nothing to hit — the fastest map, and, measured over hundreds of runs, the deadliest of the three. Someone told me one evening that they all looked the same; since then each has its own colour, and a test forbids me from ever shipping twin grounds again.
The countdown on the home screen says exactly when the map changes. Your run is recorded as a replayable trace — that trace is what feeds the leaderboard.
Your opponents are real runs
The runners on your map are not bots tuned to flatter you: they are runs actually played by other people, replayed input for input — ghosts. When you take down BadVADOR, you are beating BadVADOR’s real run, the one on the leaderboard. And posting your score sends your own run out to haunt other people’s maps: tomorrow, someone will be fighting what you did today.
On a map’s first morning, or offline, machines fill the empty seats. The game always tells you which is which — a game that dresses its robots up as humans is lying.
Playing live
The “play live” button opens today’s room: players connected at the same time as you race the same map, see each other, and collide for real. One nuance, which is a rule: a live run never goes to the leaderboard. The judge cannot replay a room full of living players, so rather than score it wrong, it doesn’t score it at all. You go there for the duel, not for the table.
Why you can’t cheat
The leaderboard doesn’t take your word for it. Your browser doesn’t send a score: it sends the sequence of your steering inputs, and the server replays it on its own machine, with exactly the same simulation code as the game. The number it keeps is the one it computed itself. So you can only lie about your own driving, which amounts to playing badly. That is why there is no account, no anticheat and no surveillance: the game doesn’t need them.
What it costs
Nothing. No account, no ads, no tracker, and nothing is for sale — I want a leaderboard without accounts to stay believable, and it wouldn’t be if a place on it could be bought. If you post a score you pick a nickname, and that’s all; the details are in the legal notice, which is in French because French law governs this service. I keep a development log too — in French as well, but the screenshots speak for themselves.