Read from the running server where it can be reached. Every one of them, with its numbers →

The table is sent rather than shipped

Shipping the weapon table with the client would mean a balance change needing a client update, and an evening of half the players on the old numbers. Sending it means changing one JSON file and restarting the server. It is the same principle the map descriptions follow: the thing most likely to want changing is the thing that should not need a build.

Ammunition is real, and it is a pool

UNSC weapons take the cartridge Halo says they take, and the reserve is a pool of that cartridge rather than a number attached to the gun. The assault rifle, the DMR and the SAW all eat 7.62×51mm, so picking up a dead man's DMR means something if you have been running the rifle.

That is why X reads the calibre out rather than a bare number. “Thirty-two of thirty-two, one hundred and sixty rounds of 7.62 by 51 millimetre in reserve” is a different sentence from “32/160”, and it is a sentence that tells you what to do next.

The reload key vents a plasma weapon rather than reloading it, because it is the same thought — make this gun able to shoot again — and somebody who has just picked up a plasma rifle should not have to learn a second key to keep using it.

Overheating is a count of rounds, not a race between two numbers

Plasma weapons never overheated, for two reasons, and both of them were underneath the weapon table rather than in it. A plasma rifle is thirty-four rounds before it lets go, which is Halo's own figure, and it always was.

Heat used to fall while the trigger was still down

Heat went up when you fired and down every tick regardless, so whether a weapon could ever let go came down to one subtraction: heat a second in against cooling a second out. Get those close and the bar sits near the bottom for ever — and it did not take a fine balance to arrange, because firing slightly slower than the arithmetic assumed made the weapon infinite. The plasma pistol fired slower than it cooled, so it could never overheat at all.

Halo's plasma weapons do not do that. They vent when you stop, and while the trigger is down the bar only goes one way. Every weapon that builds heat now waits three quarters of a second after its last round before it starts venting.

That turns overheating from a race between two numbers into a count of rounds, which is the thing a player can actually learn. Thirty-four rounds is a fact you come to know; “it depends how fast you were firing relative to the cooling rate” is not.

Three quarters of a second, because it has to be longer than the gap between taps — the plasma pistol is a tapped weapon and would otherwise vent between every shot — and short enough that letting go for a moment is a real thing to do in a fight, which is the whole decision the mechanic exists to create. Vehicle guns get it too.

And the server was throwing away half of every burst

A round that arrived twenty-two milliseconds before it was due looked the same to the server as one that arrived on time, and it discarded the first — after the client had already played the shot and spent the round. Seventy-two rounds sent, thirty-seven taken, measured.

That meant every automatic weapon in the game had been doing half its damage: the assault rifle, the SMG, the SAW, the needler, the chaingun, all of them. They now do what the weapon table says they do, so fights are considerably shorter than they used to be. Nothing in the table changed; it is just being honoured.

Melee is two moves wearing one button

A blow against a full shield is a melee. A blow against somebody whose shield has already gone is a pummel, and a pummel kills. From behind it is an assassination, and that also kills.

Halo's rule, kept exactly, and it survives translation beautifully: every weapon in the pack has a separate recording of a melee and a pummel, so telling them apart by ear tells you whether the person you just hit is about to die or about to turn round.

The server decides; the client predicts

The server owns everything that matters — where people are, whether a shot hit, how much health anybody has, what is in a chest, who won. The client predicts what it has to in order to feel immediate, and is corrected the moment it turns out to be wrong.

What is checked and what is not

• Positions are checked loosely — walls and enormous jumps, not exact speed. A strict check on a grid game over a network punishes lag far more often than it catches anybody, and the thing worth catching fails a loose check just as clearly.
• Shots are not checked for position at all, because a shot is resolved from the server's own copy of where everybody is. A client that lies about where it is has already been corrected by the time it fires.

The world is stepped twenty times a second: fast enough that a grenade travels smoothly, slow enough that a busy server is not spending all its time on arithmetic.

Sprint, and the armour abilities

Everybody sprints. Hold shift and you run, considerably faster and very much louder — forty metres of earshot against a walk's twenty-four, which is the whole of what it costs in a game where being heard is being found. A weapon heavy enough to slow you down is the only thing that refuses. It used to be an armour ability and it is not one now: see 0.9.9.3.

The armour ability slot holds Reach's set and Infinite's equipment beside it — evade, a jet pack, armour lock, camouflage, a hologram, a drop shield, a thruster pack, Promethean vision, a grappleshot, a repulsor, a drop wall and a threat sensor. While you are dual wielding you have no armour ability at all — see two guns is a decision.