transcience/docs/DECISIONS.md

Settled decisions

Design choices the user has already made, with the reasoning. Check here before asking — re-litigating a settled decision wastes a round trip, and several of these look like defaults you would otherwise pick differently.

Ordered newest last.

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Simulation shape

Game logic lives in plain RefCounted objects, not nodes. No CharacterBody2D, no Area2D, no physics server. Bullet counts make per-bullet nodes unaffordable, the dedicated server allocates nothing, and the whole suite runs with no SceneTree. Full reasoning in ARCHITECTURE.md.

Content is GDScript, not .tres. A boss is a readable diff, there are no resource UIDs churning in version control, and a test can build content inline. tools/export_content.gd writes .tres copies for inspector tuning, but code is the source of truth — port inspector edits back.

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Netcode

The client sends input and nothing else. No message exists for position, hits, damage, or a finished escape. Having no code path is strictly stronger than validating one.

Bullets replicate as spawn events, not state. ~36 bytes once per bullet; both sides run the identical integration. Only early deaths (a hit, or a wall) need announcing. Pinned by tests/integration/test_replica_parity.gd.

No lag compensation. Rewinding the world to a shooter's view would mean a player who dodged on their own screen still takes the hit. If it becomes a complaint, lag-compensate player bullets against enemies only — never enemy bullets against players.

INPUT_MAX_LEAD must stay well above INPUT_LEAD_MAX. The server's input acceptance window has to be wider than the band in which the client re-syncs its own numbering. When it was not, drifting clocks landed in a dead zone where the server silently rejected every input and the client never noticed. Pinned by tests/unit/test_input_lead.gd.

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Combat feel

Hitbox is smaller than the sprite (PLAYER_RADIUS 6 vs PLAYER_VISUAL_RADIUS 13), and PLAYER_MUZZLE_OFFSET derives from the visual radius. A visible near-miss reads as fair; an invisible hit does not.

No invulnerability frames. Every bullet that touches you lands. I-frames make dense patterns safer than sparse ones, which inverts the genre. Measured cost: ~13.6s stationary in the Warden's opening phase. spawn_grace on entering a dungeon is the sole exception, and it is a transition, not a combat mechanic.

No contact damage. Every threat is a bullet you can see and dodge. The Stalker carries a point-blank shotgun rather than damaging you by touch. tests/unit/test_content.gd asserts every hostile enemy has an emitter.

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Leaving a run

Escape is a 1-second channel that damage does not interrupt. An interruptible channel makes killing the process better than pressing the button.

A disconnect runs the same channel. The player stays in the world as linkdead, still killable. All four exits (key, menu button, clean disconnect, SIGKILL) converge on one server-side path keyed on the socket closing — there is deliberately no "clean leave" message. tools/smoke.sh asserts both the hard kill and the polite disconnect.

Boss rooms do not lock. (User, this session.) You can always walk out of a boss fight, and the boss cannot follow. The consequence: fights cannot rely on trapping the player, and disengaging is always available.

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World

Tile grid, generated layout, hand-authored boss arenas. (User, this session.) A grid because collision, line of sight and interest management all become array lookups; authored arenas because a generated boss room is a bad one about as often as a good one.

Hard fog. (User, this session.) No remembered terrain — anything outside current line of sight is not drawn, including ground already walked over.

Dungeon size scales with depth. (User, this session.) --depth N is a dev flag; what raises depth in actual play is still open.

Never send the map, or its seed. (User, this session — corrected an earlier choice of mine.) Sending (seed, depth) and regenerating client-side is far cheaper on the wire and hands any modified client the entire floor plan. Tiles stream per peer instead. The accepted trade, in the user's words: a cheater seeing further than they should is tolerable; seeing the whole map is not.

Consequence to preserve: the client holds real geometry it cannot see, because it predicts movement against walls and simulates bullets that die on them. So hard fog is a rendering rule, not secrecy. The secrecy is in what the server declines to send.

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Identity and persistence

Steam-shaped auth abstraction. (User, this session.) The goal is eventually Steam, so build the shape Steamworks uses and keep it swappable: client presents an opaque ticket, server validates it and gets a stable 64-bit account id (SteamID64's stand-in). A local dev provider persists a generated id in user://, so no Steam account is needed now.

Not integrating GodotSteam yet: it needs a running Steam client and an app ID, which would break the "no Steam account" requirement. Swapping it in later should be one provider class and no schema change.

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Progression

XP from kills, bosses worth far more. (User, this session.) A first full dungeon should give a bit more than is needed for the first level-up.

Permadeath. Death marks a character inactive — never deleted, for archival and troubleshooting — and the player picks another character or creates one.

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Characters and progression

Level 1 is base health; each level adds 10. So level 15 is PLAYER_MAX_HP + 14 * 10 = 240. Level is derived from lifetime experience rather than stored alongside it, so the two can never disagree — a hand-edited save cannot produce a level 12 character with a level 3's experience.

The five-character cap counts LIVING characters only. Retired ones stay in the store forever but free their slot. Counting the dead would lock a player out of their own account permanently after five deaths, which is not a punishment anyone signed up for.

Death unbinds the character entirely. There is deliberately no "return to the hub as the character who just died" — the run is over, so the peer is removed from the instance and left at the roster screen. The one exception is a linkdead player, which has nobody to show a roster to, so its body is left for the escape channel to resolve as before.

Experience is shared across the party, undivided. Everyone alive in the instance receives the full amount for a kill. Splitting it would make bringing a friend cost you progress, which is the opposite of what the hub roster exists to encourage.

A level-up heals by the amount it added. Gaining a level mid-fight should feel like relief, not like the bar you were watching got further from full.

The character store refuses to start rather than starting empty. A corrupt or unreadable save aborts the server. Loading empty would look like it worked and then overwrite every character on the first level-up.

Account ids are written as decimal strings in JSON. They are 64-bit and JSON numbers are doubles, which would silently round them.

Character swapping is hub-only, enforced on the server. Swapping inside a dungeon would be an instant, uninterruptible exit from danger — strictly better than the one-second escape channel, and it would make that channel pointless. The menu greys the button out so the rule is visible, but the server refuses regardless of what any client's UI allows.

Health regenerates at 0.5% of MAXIMUM per second, with no out-of-combat gate. A percentage rather than a flat rate, so it does not become irrelevant at level 15 — a capped character regains 1.2 hp/s against a level 1's 0.5, and both take about 200 seconds to heal from nothing. No combat gate because at this rate it cannot out-heal anything actually shooting at you, and a trickle that never stops is easier to reason about than a timer players have to learn.

A dead character is gone, as far as the player is concerned. Retirement is the server's own bookkeeping for archival and troubleshooting; the roster the client receives contains living characters only. Listing the dead would offer a choice that cannot be taken.

Experience rides the snapshot, not the character roster. The roster is only re-sent when the set of characters changes, so a bar fed from it moved only on level-up or a swap. The live total is four bytes on a message that already goes out at 20 Hz.

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Inventory and loot

Four slots, permanently on screen. An inventory you have to open is a menu, and a menu is a death in a game where the floor is bullets. INVENTORY_SLOTS is one constant that the wire format, the save record and the HUD all read, so growing it is a one-line change — but not into a paged or scrolling UI.

Item actions ride the input frame rather than becoming new messages. InputFrame gained BTN_USE, BTN_DROP and a slot byte. Using an item happens during a fight, so it has to be ordered against movement on the same tick and be as cheap to reject as a movement vector. Riding the existing stream gets the redundancy that covers a dropped packet, the replay guard on last_input_tick, and a rate limit of one action per tick for free. A separate reliable RPC would have needed every one of those bolted back on.

Item actions are edge-triggered; movement and fire are not. The client resends its last few frames every tick and a starved server coasts on the last one it holds, so a level-triggered read would empty the whole inventory in four ticks. The slot is part of the edge as well — tapping 2 while 1 is still held is a second, distinct action rather than a swallowed one.

Loot has two visibilities, and the instanced one is enforced on the wire. World-shared loot is one entity the first player to reach it takes. Player-instanced loot is one entity per eligible player, and a peer is never told the other copies exist — the filter lives in NetCodec.encode_snapshot beside the actor interest radius, not in the client. It is an interest-management rule, not a UI convention.

The Warden's Ration is useless on purpose. It is dropped by every boss, one per player who was alive for the kill, and does nothing when used. Its job is to make sure the player-instanced path runs on every single boss kill instead of being a code path nothing exercises. If it ever gains an effect, that job needs a new holder.

Anything dropped becomes world-shared, whatever it was before. An instanced trophy you do not want should be able to reach someone who does — otherwise "droppable" means nothing for half the items in the game.

A potion used at full health is refused, not spent. Nobody drinks one on purpose at full health, so a mistimed keypress must not do it for them. The useless ration, by contrast, is consumed: "does nothing" has to mean a completed transaction or it proves nothing about the path it exists to test.

A full bag leaves the item on the floor. Nothing is destroyed by a failed pickup, and the failure does not block the portal, which shares the interact key.

Inventories live on the character and are written on every transaction. Not on a timer: a crash between "picked it up" and "wrote it down" must not be a way to lose an item, or — far worse — to duplicate one. They are stored as item ids rather than wire indices, so a save survives Items.ORDER being appended to, and an id this build does not know decays to an empty slot rather than to the wrong item.

Items do not stack. One id per slot, no count, no charges. Everything the game currently needs fits that, and the wire format, the save record and the UI are all simpler for it. Add a count when something actually needs one.

Ground loot never expires; each world caps at MAX_LOOT_PER_INSTANCE, oldest evicted. Dungeons close and take their litter with them, so only the hub — which never closes and where players can drop things — can realistically reach the cap.

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More than one dungeon

A second dungeon is a set of multipliers over the shared content, not a parallel copy of it. DungeonDef scales enemy health, boss health and loot chance; the generator, the rooms, the enemy mix and the boss are the same objects the real run uses. A duplicated Content would drift from the original the first time anything was tuned, and the whole value of the Proving Grounds is that it is identical apart from the numbers.

It is reachable from the hub rather than hidden behind a launch flag. A flag would need a server restart to switch, which makes comparing the two a chore and makes "does this behave the same in the real run?" a question nobody bothers to ask. Two portals a few metres apart makes it a five-second check.

Which dungeon you enter is decided by where you are standing. The portal is resolved server-side from the player's own position, and the PORTAL_USED event carries the answer. There is deliberately no client message that names a dungeon: one would let any client ask for the Proving Grounds' loot rate and walk out with it.

The instance matcher compares dungeon ids. A forming run only accepts party members who asked for that kind. Without it, walking into one entrance could drop you into the other's run purely on timing.

Scaling clamps at both ends. Health never scales below 1 — a creature with zero health is a crash waiting for a divide — and a boosted drop chance never exceeds certain, or the roll becomes dead code and "chance" stops meaning anything.

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Upgrades

Damage is base × (1 + Σ additive) × Π multiplicative. The flat +5% every upgrade carries, Spread's −10%, Doubleshot's −50% and Glass Cannon's +100% pool into the additive term; Sniper's ×2 multiplies the result. The brief called Sniper out as multiplicative specifically, and this is what that buys: it stays worth taking however many percentages have already piled up, and two Snipers is 4× rather than +200%.

The +5% belongs to taking an upgrade, not to any particular upgrade. It lives in SimConfig.UPGRADE_DAMAGE_BONUS and is applied once per upgrade held, rather than being baked into seven definitions where it would be seven places to get wrong.

A character record becomes a live player in exactly one place. ServerRuntime._adopt_character, called from _place, which every transfer goes through. SimWorld knows nothing about characters and hands back a blank player on every instance change, so something has to give it back its level, upgrades and bag — and for a long time only character select did. Every portal and every escape reset the player to level 1 with base stats and an empty inventory, while the record on disk stayed correct, which made it look like a display bug.

Stats are derived from the upgrade list, never stored. PlayerStats.build() recomputes them from the ids the character holds, the same way Progression derives level from experience. One source of truth means a saved stat can never disagree with the upgrades that produced it.

Glass Cannon halves the LEVELLED maximum health, and multiplies if taken twice. Half of base HP would be a flat −50 that fades from brutal at level 1 to nearly free at level 15, which is the wrong direction for a drawback.

Poison doses stack independently rather than refreshing. Chosen over the alternatives knowing it is by far the strongest reading: at ~4.3 shots/sec that is dozens of concurrent doses. It costs nothing to run because every dose lasts the same number of ticks — so they expire in the order they were added, the pending expiries are a plain FIFO, and only its front is ever examined.

Split Shot's children leave at ±45° from the original heading, 90° apart, and are born just past the target rather than on it. A child spawned inside what was just hit would be resolved against it again on the same tick — a free second hit, and with several charges a free chain of them.

Level-ups queue. Reaching two levels in one run owes two choices. Losing one for doing well is a punishment nobody would guess at.

The offer is rolled once and held on the character. If it regenerated when the screen opened, closing and reopening would be a free reroll and everyone would press it until a legendary turned up. It is written to disk with everything else, so a crash is not a reroll either.

Upgrades are spent standing at the hub NPC, enforced on the server. Same rule as the dungeon portal: where a player is standing is the one thing a modified client cannot fake. The screen closes when you walk away so it never offers a button that would be refused.

Bullet speed has a hard ceiling. Wall collision samples a position once per tick, so anything faster than one tile per tick tunnels through geometry. Two Snipers would ask for 2480 u/s against a 1920 threshold, and a tunnelling bullet looks exactly like a bullet — so MAX_BULLET_SPEED clamps it and a test pins the clamp.

Poison ticks are not announced as hits. They land many times a second on a reliable channel, and the client learns enemy health from the snapshot anyway. Death is still announced, because the experience award is keyed on that event and a kill by poison has to score.

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The scale of the numbers

Health and damage are ten times what they started as, and every ratio is unchanged. A shot is 60, a fresh character has 1000, the Warden has 36000, and enemy health and emitter damage were scaled with them — time to kill is exactly what it was.

The reason is rounding, not balance. Damage is an integer, and at a base of 6 the +5% that every upgrade carries computed to 6.3 and rounded back to 6: a player took their first upgrade, was told it made them stronger, and it did nothing. Ten times the base means every 5% step is worth 3 damage. The same applies to the boss's per-phase armour multiplier, which at 6 damage rounded 1.15 into 1.17.

The practice dummy is indestructible by flag, not by a large number. The old 100000 health was already past the u16 the snapshot sends enemy health in, and once a shot did 60 a patient player could have worn it down and left the hub without a practice target until the next restart. A flag says what was actually meant.

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Bosses that move, and attacks that warn

Movement belongs to the phase, not to the boss. A fight that stands still and then starts hunting you is one boss with two phases. BossDef.stationary was removed rather than kept alongside the phases: a flag claiming the boss stood still while one of its phases walked around would be a second source of truth, and the wrong one. BossDef.moves() is derived.

CHASE holds a distance instead of closing. A boss standing on top of a player is a boss whose bullets cannot be read, and this genre cannot afford that. It backs off when you come inside its preferred range.

Waypoints are fractions of the arena. The Warden's hall and the Choir Vault are different sizes, and a phase written against absolute coordinates would only work in one of them.

The boss room clamp moved after movement. It was a no-op while every boss was stationary. Boss rooms deliberately do not lock, so walking out is always an escape — which is only true if the boss cannot follow.

Telegraphed strikes are announced by a stateless emitter. Emitters are shared resources, so nothing may be remembered between the warning and the strike; the positions are derived from the volley number instead, and a test asserts the burst lands where the marker promised.

Telegraph markers are drawn through fog and through walls, unlike every other thing in the view. A warning you cannot see is an unavoidable hit with extra steps, which is the opposite of what a telegraph is for.

Each boss has its own entrance in the hub. A dungeon names the arena it ends in, and the arena decides the boss. Which fight you are walking into is the one thing a player chooses before a run, so it is not rolled for them — not from the depth (a dev flag nothing in play raises, which left the second boss unreachable) and not from the seed either. Only the Proving Grounds leaves it open, because a harness you re-enter every couple of minutes wants whichever fight comes up first.

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Bullets do not animate

One frame, and a slow turn. The bullet sheet's eight frames are a colour cycle rather than a shape change, and running it meant every bullet on screen strobed through a palette in unison — genuinely hard to look at with a few hundred in the air, which is the normal case for this game.

Each bullet now holds one frame and rotates at Art.BULLET_SPIN_RATE, offset by its own id so a ring of twenty does not turn as one rigid wheel. The rate is slow enough that nothing completes a full turn inside its own lifetime, so it reads as drift rather than as spin — a test pins that against the longest-lived bullet in the game.

The other seven frames stay in the atlas because that is what the source art is. Nothing draws them, and the renderer now slices four textures at startup instead of thirty-two.

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Settings

Preferences are local to the client and nothing else knows about them. Which key fires produces the same [InputFrame] either way, so the server has no opinion and never hears about it. Settings is static for the same reason GameOpts is: a --script tool has no main loop and cannot resolve autoloads.

Bindings are stored as physical keycodes and labelled through the active layout. Physical is what tools/setup_input_map.gd already uses, so bindings follow key position; translating the label back means an AZERTY player reads the letter printed on the key their fingers are on. The translation is skipped on a display server with no keyboard — headless does not merely lack the call, it logs an engine error and hands the argument back, and there is no feature flag to test for.

A rebind replaces every event on the action, not just the first. Keeping the alternates would mean the action still answered to the key you just moved away from, which reads as the rebind not having worked. The cost is that rebinding movement loses the arrow keys; untouched actions keep all their defaults.

One key doing two things is refused, and the clash is named. Silently accepting it produces a control scheme that is broken in a way the player has to diagnose themselves.

"Reset" restores what the PROJECT shipped, captured once before anything overrides it. Captured later it would restore the last session's choice — that is, the thing the player was trying to undo.

Panels are the pack's shape in this game's colours. The set is cream throughout, which is right for buttons — they are meant to be the bright thing you press — and wrong for a dialog laid over a dark dungeon. The panel stylebox is modulated dark, which keeps the pixel border and the corner shape and lets every label the game already draws in light colours stay readable. The alternative was recolouring every label in five screens to suit the art.

A card's rarity is its frame, not a word on it. Three upgrade choices are compared at a glance, and a colour reads faster than a label.

Effects play on an SFX bus created at runtime. A bus layout resource would be one more file to keep in step with the code that reads it, and the sliders being real mixer settings beats multiplying a number into every play() call.

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Drawing a boss that moves

The boss is interpolated between snapshots like every other actor. It was not — boss_state() handed back the newest snapshot raw, so the boss stepped at the 20 Hz snapshot rate rather than the frame rate. Invisible for as long as every boss stood still, and the first one that moved looked broken. Not interpolated across an instance change, though: the previous snapshot describes a different fight in a different room.

A CHASE boss has a dead band around its preferred distance. The correction is signed, so without one the sign flips every tick at the standoff and the boss vibrates on the spot at the tick rate — a couple of pixels, and unmistakable.