Space Defender

The gun is not the resource — the flight time is

The readability limit is arithmetic, not a feeling

A pattern you cannot outrun is not difficulty

A boss whose guards cannot lift is a boss nobody can kill

Armoured plates cannot be damaged while a core beside them is alive, which gives each fight an order to solve while you dodge. But a guard graph that unwinds perfectly can still be a geometric deadlock, and the Keystone shipped as one: its third core sat directly above a plate only that core could open, so every bolt that could have reached it was absorbed on the way up. The graph was sound and the geometry was not — a confident answer to the wrong question. Every boss is now checked by firing a bolt up every column that matters, and the check is kept honest by being run against the broken version, which it rejects.

Local play

Everything runs in this browser. There is no sign-in, no leaderboard and no account: your settings, your bests and which Daily runs you have flown are kept in local storage under this route’s own keys, and clearing this game’s data leaves every other Zerdly tool alone. You fly with 3 shields, and a hit buys a moment you cannot be hit again so that one bad second cannot take all of them. Every craft destroyed without being hit adds 30 to the next, up to 12 deep.

Questions

Why does the gun have barrels instead of a fire rate?

Because a fire rate is not a decision. With an auto-repeating weapon the optimal play is to hold the trigger down for the whole game, and the only skill left in the route is dodging. Here each of the 3 barrels is occupied by its own bolt until that bolt hits something or leaves the top of the field — so the cost of a shot is how long it spends in the air. Measured: sustained fire into the front rank is 5.2 bolts a second, and sustained missing is 3.6. Picking your shots is worth 44% more of them.

So a miss is punished twice?

Yes, and deliberately. In time, because the bolt flies the whole field before its barrel is free. And in points, because the bonus for finishing a wave is mostly your accuracy. The two halves of the design say the same thing to the player instead of pulling in opposite directions — a route that made a miss cheap in one currency and expensive in the other would just be confusing.

How fast can an enemy bolt travel?

No faster than 1.19 field-heights a second, and that number is derived rather than chosen. A bolt is readable when you can still get out of its way after seeing it: 250 milliseconds to react, plus 87 milliseconds to move far enough sideways that it misses the hull — 337 in total — over the distance a bolt fired from the lowest legal altitude has to fall. Difficulty climbs from 0.66 toward that ceiling and never passes it. Type the number in by eye instead and the hardest wave becomes a coin flip that looks like difficulty.

Can something shoot me from off the screen?

No. Nothing off the field may fire, and nothing below 48% of the field height may fire either — that is the same rule seen from the other end, because down there no warning distance is left to give. Craft that have flown off the edge show a marker on the side they will come back through. Diving and flanking craft are dangerous because they will fly into you, not because they shoot from under your guard.

Can a dive be dodged, or is it a coin flip?

It can always be dodged, and that is measured rather than asserted. A dive resolves its target once, when it commits, from where you are and 0.42 seconds of the direction you are already moving — it does not chase you afterwards, so changing direction beats it. Its sideways travel is front-loaded, so the last stretch before it reaches you is very nearly vertical: across every rank, every starting column and the full width of aim points, the worst case still drifts less than a third of the distance you can move in the same window. A pattern you cannot outrun is not difficulty, it is a coin flip — and because it looks like a hard attack rather than a broken one, it is the defect this genre is most likely to ship.

What does Overdrive actually do?

It doubles the battery from 3 barrels to 6 for 4.5 seconds. That does not make you shoot faster at what you were already shooting at — it makes the expensive targets affordable: the warden behind two drones, the segment on the far side of a boss. It is charged by damage dealt, so the only way to earn it is to be doing the thing it rewards. The first draft made a hit free its barrel sooner, which was dropped because the base rule already does exactly that, and an ability that repeats the base rule is not an ability.

Is the toughest craft the most dangerous one?

No, on purpose. A warden takes 3 bolts and fires slowly; a lancer takes 2 and has the fastest gun up there — and it fires two bolts down the same column a beat apart, so stepping aside is not enough, you have to stay aside. If the tough one were also the dangerous one, "what do I shoot first" would have no wrong answer and there would be no reason to have more than one kind of enemy.

Can a boss be impossible to kill?

Not any more, and one was. The armoured plates cannot be damaged while a core is alive, which gives the fight an order — and a guard graph that unwinds perfectly can still be a geometric deadlock. The Keystone shipped with its third core sitting directly above a plate that only that core could open, so every bolt that could have reached it was absorbed on the way up. Every boss is now checked by firing a bolt up every column that matters and asking whether each segment can ever be the first thing in its path. The check is kept honest by running it against the broken version, which it correctly rejects.

Are the formations generated?

The shapes are not; what they are made of is. All 8 formations are 8 by 4 arrangements somebody drew, because a procedurally-placed formation looks procedural every time and a wave shooter lives on whether the wall in front of you reads as an intent. The seed decides which slots hold a drone, a lancer or a warden, and which craft sorties when — the two things you actually have to answer.

Do the modes actually differ?

Campaign, Endless Waves, Boss Rush, Daily Seed. Campaign is 12 waves with a boss every 4; Endless never stops and keeps sharpening; Boss Rush is bosses back to back with no formation to warm up on; and the Daily is seeded by the UTC date, so it is the same run for everybody who flies it that day.

Can a bolt pass through a craft?

No. The simulation runs at a fixed 180 steps a second whatever the display is doing, and the fastest thing on the field moves 7.9 thousandths of a field in one step — against craft 52 thousandths wide. Collisions are resolved in pool order rather than by proximity, which is what lets a Daily replay reproduce exactly: two craft overlapping the same bolt on the same step always resolve the same way.

Can I play without a mouse?

Yes. Arrow keys or A and D fly the ship, space or W fires, Shift spends Overdrive, and there are held buttons under the field as well. On a phone, dragging on the field flies the ship and the gun fires itself — that version is one-handed but gives up the barrel decision, so it can be turned off in settings if you would rather keep the trigger.

What is stored about me?

Nothing that leaves this browser. Your settings, your best for each mode and which Daily runs you have flown are kept in local storage under this route's own keys, and clearing this game's data leaves every other Zerdly tool alone. No wave in progress is ever saved — the seed is stored and the waves are rebuilt from it, so a run can never resume onto a path nobody approved. There is no sign-in and no leaderboard, because there is no server to hold one.

Related interactives

• Traffic Escape — The other route about being in the wrong lane at the wrong moment.
• Brick Breaker — A wall you take apart, and a paddle that aims.
• Zerdly Bubble Shooter — Where a shot is a commitment and the ceiling comes down.
• Reflex Grid — The route that measures the quarter-second this one designs around.