Zerdly

Boat Racer

Powerboat racing where the world pushes back: real currents, shallows and channels that narrow. 8 waterways, 5 modes including a slalom and a daily course.

Pick a race

Waterway

How a race works

Steering

  • ↑ or W opens the throttle, ↓ or S goes astern, ←→ work the helm.
  • P pauses, R restarts. On a phone the wide ▲ button is the throttle.
  • A boat has no brakes. Closing the throttle is the only way to slow down and the water does the rest, so lift early for a bend. The astern pedal is for a real overshoot, not for slowing down.
  • A rudder needs water flowing past it. A boat lying still cannot steer at all, and the faster it goes the harder it turns — the opposite of a car, where the tightest circle is available at a crawl. Full helm is always as hard as the boat can turn right now, whatever that happens to be.

The current, and what it is worth

  • The arrows on the water are the water. Each one shows where the flow would carry a drifting boat in two seconds, and it is the same number the simulation uses — not a decoration drawn beside it.
  • A cross-set pushes you off the line you are holding. Aim at the buoy and you arrive downstream of it; point a little up-current and you arrive at it. The readout says how many metres the water will move you in the next five seconds.
  • It is worth most where the channel is narrow. We measured it: on Mill Race — eleven metres wide with the hardest set in the set — steering up-current is worth about 1.5% of a lap, and steering the wrong way costs 6% and puts you on the bank nine times. On Broadwater, which is open and still, it is worth nothing at all.
  • On wide water you can ignore it and still get round: your own corrections bring you back. What you lose is your position in the channel, and that only turns into time when there is a bank close enough to matter.

The waterway

  • Buoys must be passed in order, so cutting across does not shorten a lap. The gates are wider than the water, so any line through the channel counts.
  • Touching a bank runs you aground: you keep about 45% of your speed and lose whatever was carrying you into the mud. Nothing else happens — it is not a penalty, it is just slow.
  • Stretches of shallows, weed bed, chop slow the hull and, in the shallows, blunt the helm as well.
  • Flat out in open water is about 91 km/h.

Modes

  • Sprint — One run from the start buoy to the finish, point to point. 5 rivals, 1 lap.
  • Circuit — Three laps of a closed waterway against rivals. 5 rivals, 3 laps.
  • Slalom — Pass each buoy on the side it says — left, then right, then left. Miss a side and it costs you time. 5 rivals, 2 laps.
  • Time Trial — No rivals. Your own best run drives alongside you as a ghost, and restart is one key away. 2 laps, alone.
  • Daily Waterway — One generated waterway for everybody, changing at midnight UTC. Same seed, same water. 5 rivals, 2 laps.

Slalom

  • Each buoy says which side to pass it: port, then starboard, then port, all the way round. Getting one wrong adds 3 seconds to your time — it is never a lost lap, and the results screen shows both the raw time and the one the placings use.

Rivals

  • Rivals sail the same boat you do, with the same thrust, the same drag and the same rudder. A harder rival lifts later, holds a steadier line and steers for the water; a novice aims straight at the buoy and gets pushed off it. None of them is given a bigger engine, and none catches up because you are ahead.

Your data

  • Best times, ghosts and settings are stored on this device only. Nothing is sent anywhere, and clearing this game leaves the rest of Zerdly alone.

The water costs you position, and only sometimes time

A boat goes where the water takes it, plus where it is pointed. Aim straight at a buoy in a cross-set and you arrive downstream of it. Point a little up-current and you arrive at it.

We measured what that is worth, and the honest answer is it depends on the channel. On Mill Race — eleven metres wide with the hardest set in the set — steering up-current is worth about 1.5% of lap time, and steering the wrong way costs 6% and puts you on the bank nine times. On Broadwater, which is open and still, it is worth nothing at all. Over all 8 waterways it averages 0.2%.

The reason the average is small is worth knowing: your own corrections already compensate. Steer at the buoy and being pushed off line makes you turn back toward it, so you get round anyway — you simply sit further from the middle of the channel the whole way. Measured: 4.40 m of average distance off the line against 3.17 m for a boat that steers for the water. In eleven metres, that gap is the bank.

How to play

Arrows or WASD work the helm and the throttle. P pauses and R restarts. On a phone the wide button in the lower corner is the throttle.

There are no brakes. Closing the throttle leaves the water to slow you, so lift early for a bend. The astern pedal is for a genuine overshoot.

A rudder needs water flowing past it. A boat lying still cannot steer at all, and the faster it goes the harder it turns — the opposite of every car. Flat out is about 91 km/h, or 49 knots, and the tightest circle at that speed is 28 metres across against 6 at a crawl.

The arrows on the water are the current. Each shows where the flow would carry a drifting boat in two seconds, and the readout says how many metres it will move you in the next five.

The hazards are the water, not objects

There is nothing to pick up and nothing to dodge. Shallows add drag and blunt the helm, weed is drag without much loss of steering, and chop off a shore is a little of both — all handled in the physics, so a hazard changes how the boat behaves rather than firing an event at you.

The banks are real geometry. Touching one runs you aground: you lose about 55% of your speed and whatever was carrying you into the mud, then carry on. No current anywhere runs faster than 3.2 metres a second, which is well under the speed a boat can make against it — so no part of any course is unreachable however the water is running.

Modes

Sprint
One run from the start buoy to the finish, point to point. 5 rivals over 1 lap.
Circuit
Three laps of a closed waterway against rivals. 5 rivals over 3 laps.
Slalom
Pass each buoy on the side it says — left, then right, then left. Miss a side and it costs you time. 5 rivals over 2 laps.
Time Trial
No rivals. Your own best run drives alongside you as a ghost, and restart is one key away. 2 laps, alone.
Daily Waterway
One generated waterway for everybody, changing at midnight UTC. Same seed, same water. 5 rivals over 2 laps.

Tips

  • Lift before the bend. With no brakes, the only way to make a tight bend is to have stopped accelerating a long way before it.
  • Watch the channel, not the current. Where the water is wide you can ignore the set. Where it narrows, point up-current before you are pushed rather than after.
  • A bend costs a boat far more than it costs a car. Halving the radius halves the speed you can hold, where a car loses about a third.
  • Never steer the wrong way for a set. The harness measured that at 6% on a narrow course — worse than ignoring the water entirely.

Privacy and local play

Everything runs in your browser. There is no sign-in, no server and no gameplay API: your best times, ghosts and settings are stored on this device only, under keys belonging to this game alone, and clearing them does not touch anything else on Zerdly.

Questions

Does steering for the current actually make me faster?
Sometimes, and we measured it rather than assuming. Bots with identical boats raced three steering policies over all 8 waterways. On the narrow courses steering up-current is worth about 1.5% of lap time, and steering the wrong way costs 6% and puts you on the bank repeatedly. Averaged over every course it is only 0.2%, because on open water your own corrections bring you back anyway. What ignoring the water really costs is position: 4.40 m of average distance from the middle of the channel against 3.17 m.
So why bother with the current at all?
Because position turns into time as soon as there is a bank close enough to matter. In an eleven-metre channel, sitting a metre further off the line is the difference between a clean lap and three groundings. The wide, open courses are where you can safely ignore it — and the arrows tell you which kind of water you are on before you find out the hard way.
Is the arrow on the water the real current?
Yes, and that is a guarantee rather than a promise. There is one function that answers 'what is the water doing here', and the simulation and the drawing both call it. An arrow two metres long is water doing two metres a second — the same number that moved your hull on the last step.
Why can I not turn when I am stopped?
Because a rudder works on the water flowing past it. A boat lying still cannot steer at all, and the faster it goes the harder it turns — the opposite of a car, where the tightest circle is available at a crawl. At walking pace the tightest circle is about 6 metres across; flat out it is 28. Full helm is always as hard as the boat can turn right now, so the controls never feel dead and never spin you.
Where are the brakes?
There are none, and that is the rule the whole route is built on. Closing the throttle leaves the water to slow you, which it does — quickly at the top of the range and much more slowly further down. The astern pedal is weak on purpose: it is for a real overshoot, not for slowing down. The way to make a gate is to lift early.
What happens if I hit the bank?
You run aground: you lose about 55% of your speed and whatever was carrying you into the mud, and you carry on. It is not a penalty and it does not end your race — it is simply slow. The shore is real geometry, and the collision is solved along the path your hull actually travelled rather than sampled at the end of a step.
What do the coloured patches of water do?
They change how the boat behaves and nothing else. Shallows add a lot of drag and blunt the helm — a keel in shallow water is fighting its own wake — so flat out over them is about 66 km/h instead of 91. Weed is drag without much loss of steering, and chop off a shore is a little of both. There is nothing to collect and nothing to dodge.
How does Slalom score the sides?
Each buoy has a side it must be passed on — port, then starboard, then port, all the way round. Getting one wrong adds 3 seconds to your time, and the results screen shows both your raw time and the one the placings use. It is never a voided lap: a rule that silently deletes a lap is one a player cannot see.
Can the rivals cheat?
No. Rival boats run through exactly the same physics as yours — the same thrust, the same drag, the same rudder curve. What a difficulty setting changes is what they do with the helm: how late they lift, how steady a line they hold, and whether they steer for the water at all. A novice aims straight at the buoy and gets pushed off it, which is the same mistake you can make. Nothing about being ahead or behind changes their speed.
Is the Daily the same for everyone?
Yes. The waterway is generated from the UTC date and nothing else, so two people on opposite sides of the world race the same water on the same day. Every generated course is checked against the boat — a navigable width the whole way round, and one bend tight enough to matter but never tight enough to be impassable.
Does reduced motion make it easier?
No. It swaps the chasing camera for a steady view of the whole waterway and calms the effects; it changes no rule, no timing and no result. The route also follows your operating system's reduced-motion setting automatically.
Why is there no leaderboard?
There is no server and no account, so there is nobody to compare you with. Your best times, ghosts and settings live in this browser and nowhere else.

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