Byte count used when copying entity state data during initialisation / room changes.

Byte count used when copying game-state data during initialisation / room changes.

End pointer for the entity-state backup region used by copy routines.

Set by the main menu (MainMenu_ChooseLearnerOrSuper): 00 = Super Berk, 01 = Learner Berk. Print_StatusMessages uses this to choose the rating message at Messaging_TooLateIveChangedMyMind.

Address of the complex state data for the entity involved in the last collision / interaction check. Written by the collision helpers at F2B2, F31F, F381 and F3E3; read as IX / IY / BC throughout Berk's movement and pick-up / put-down logic.

Address of the complex state data for the entity currently being processed (usually Berk). Often the entity Berk is holding when bit 04 of Berk's flags byte 3 (IX+03) is set.

Index of the current Bad Tempered Thing task (meal request).

Phase / sub-step within the current task.

Index of the current dialogue / message line.

Pointer into Berk's current script data stream.

Cross-cutting event bits for trap door and task state.

Bit	Meaning
00	Room / script event raised (set by helpers such as Script_Shared_SetEventBit)
01	Trap door is open / trap door event armed
02	Falling-entity latch (cleared/set by Process_Falling_Entities)
03	Object has been offered to the trap (Bad Tempered Thing path)
04	Task-two / upstairs event latch
05	Reserved / unused in the observed call sites
06	Special put-down / room-transition event
07	Task entity script is active

Per-task status bits (Drutt / collectible progress and dialogue gates).

Bit	Meaning
00	Task progress / dialogue gate
01	Timed Berk event pending
04	Drutt collected a type-18 object
05	Drutt collected a type-1C object
06	Berk action / eat latch
07	Berk script / dialogue busy

Flags for the "Thing Upstairs" (task two) state machine.

Bit	Meaning
01	Task-two script should advance
02	Spawn / random-walk latch for the upstairs helper
03	Helper entity needs its layout restoring
04	Task-two helper busy
05	Task-two helper secondary latch
06	Task-two room-transition latch
07	Task-two entity script active

Flags for the task-three (boiled slimies / feeding) state machine. Bit names below are taken from the Bad Tempered Thing dialogue gates and the stove / put-down writers that set or clear them.

Bit	Name	Set / clear
00	MobileHeater	no SET/RES site found
01	Slimies	set by F110; tested by D901
02	SlimyLoose	set by B401 / C6FC; cleared by Update_Stove
04	BoilEmUp	set by ScriptRoutine_TaskThreeBerkRightWindow_SetFlagsAndLayout; cleared by Update_Stove; tested by D927
05	BoilEmUpLatch	set by ScriptRoutine_TaskThreeBerkRightWindow_SetFlagsAndLayout; cleared by Update_Stove / C397
06	StoveReady	set by Update_Stove when StoveTick reaches 04
07	StoveUpdated	set by Update_Stove; tested by ScriptRoutine_TaskThreeBerkRightWindow_SetFlagsAndLayout

Flag byte for task-one progress messages (Table_TaskProgressMessagePointers) and the type-08 / type-0B collision latch at Check_Entity_Collision.

Bit	Meaning
06	Third consecutive Check_Entity_Collision collision (cleared by EDB8)
07	Collision seen this check (Check_Entity_Collision)

Cross-cutting interaction bits for crushers, ghosts and hazards. Meanings below are from observed writers/readers only.

Bit	Meaning
01	Set by B34B; tested by D93E
02	Set/cleared by ScriptRoutine_TaskFourTickOfferItem; tested by D95C to gate dialogue
03	Set by Update_Ghosts_RetriggerBit3; tested and cleared by Update_Ghosts
04	Set by Update_Crusher; tested by D944 to gate dialogue
06	Set by Update_Crusher when SharedTick reaches 03; no BIT reader found
07	Set by Update_Crusher on every crusher update; no BIT reader found

Animation and interaction bits for the trap door itself.

Bit	Meaning
01	Weight-chain layout swap pending
02	Drutt is mid trap door animation
03	Trap door is open for Berk's put-down check

Frame counter driving Drutt's animation.

Count of collectible eyeballs gathered so far.

Byte used by collision / collectible helpers (Check_Entity_Collision, Update_Bad_Tempered_Thing_Dialogue) to remember a room index or entity field across a call.

How many times Update_Stove Update Stove has run this boil cycle. On the fourth call that routine sets StoveReady (bit 06 of TaskThreeFlags).

Non-zero while a room transition is in progress.

Countdown / tick used when spawning transient entities.

Shared animation frame counter for scripted entities.

One-byte counter shared by Update_Crusher (increments on each crusher update) and script routine ScriptRoutine_TaskFourTickOfferItem (decrements toward zero). Not a pure frame counter: Update_Crusher advances it once per crusher call, and when the value reaches 03 that routine also sets bits 06 and 07 of EntityInteractionFlag.

Countdown timer for task-three creature behaviour.

State of the stove / heater prop.

Latch that triggers the next on-screen message.

Global frame counter advanced by the main loop.

State flags for the Bad Tempered Thing.

Lock that prevents Berk starting a new action until cleared.

Bit 07 marks a task slot as used. Task 05 is chosen separately at AC10.

Non-zero while a timed Drutt / trap door script is armed. Set to 01 by ScriptRoutine_StartDruttScript, written from an entity type at ADED, cleared by Update_Timed_Events, and tested by Update_Berk_State_ActiveTaskFrameTick / B973 before those paths run.

Live script-data cursor while a task / entity script runs. Task updaters copy their dedicated script position (Pointer_TaskThreeScriptPosition / Pointer_DruttScriptPosition / Pointer_TaskTwoScriptPosition / Pointer_TaskFourScriptPosition / Pointer_ThingUpstairsScriptPosition / Pointer_BerkScriptPosition) here, call the shared runner, then write the (possibly advanced) cursor back.

Pointer into task-three script data.

Pointer into Drutt script data.

Pointer into task-two script data.

Pointer into task-four script data.

Script cursor for complex entity slot 20 when its type is 22. Written by BDBA / BC2B; read by BC1F.

Pointer to the entity Berk is currently holding.

Current score.

Three 3-byte records used by Update_Collectibles Update Collectibles. Each record is a script-position word plus a per-slot counter; Update_Collectibles walks the table, copies a record through Pointer_ActiveScriptCursor / CollectibleCounter, calls Collect_Entity, then writes the updated values back.

Room index remembered by ED36 while Berk opens a door behind him. Also used by AFC5 as the exclusive end address when measuring the CurrentTaskIndex…72E7 game-state backup length into CopyLength_GameState.

Y-extent to restore onto a held entity. Written by B6D8 as the collision partner's y−01 during Berk's put-down / pick-up probe; read and cleared by ScriptRoutine_PickUpHeld when applying the held entity's new y / y-extent.

Selects which display buffer is active when swapping primary / secondary.

Attribute used when printing messages.

Short countdown used by ScriptRoutine_BerkDoorBehind. Set to 01–02 at ED9B after a room change; while non-zero ED19 decrements it and skips the rest of that interaction pass.

Camera Y coordinate.

Camera X coordinate.

Task timer. Incremented at AC65. AC69 compares it with A0 for the timeout path. Update_Berk_State_AttrStripFromSeed also reads it for the status attribute strip. Reset to 00 at AD48. Not the pseudo-random seed at RandomSeedScratch.

Cleared at E2A4 and loaded at E2C6 from the byte at the address the message stream names. AE6A returns if it is zero. Otherwise each pass of the loop at Update_Timed_Events_HeldCountdownStep sets the bonus at Pointer_BerkHeldEntity, reprints it and calls Handle_Berk_Action.

Game tick counter.

High score.

Pointer to the current display-buffer base used while drawing layouts.

Base x/y character coordinates used while processing graphic layout data (H = x, L = y).

Pointer to the character set currently used for text output.

Pointer to the camera room origin used while drawing.

Script-data address saved by ScriptRoutine_StartScriptLoop so ScriptRoutine_EndScriptLoop (End Script Loop) can reload HL and repeat the body while ScriptLoopCounter remains non-zero.

Saved position in graphic layout data at the start of a loop (opcodes EE / EF).

Remaining iterations for a script-level loop. Loaded from the operand of ScriptRoutine_StartScriptLoop; decremented by ScriptRoutine_EndScriptLoop until it hits zero.

Remaining iterations for the current graphic layout loop (opcodes EE / EF).

Copy of Berk's X coordinate used by camera-follow logic.

Copy of the camera-follow entity's x-extent (IX+08), written by Update_Berk_Controller alongside BerkXCoordinateCopy. Not a Y coordinate.

Copy of Berk's room index used by camera-follow logic.

Index of the graphic set currently selected by graphic layout opcode F4. Written into the display buffer with each tile; Blit_DisplayBufferRow looks up the set base in Table_GraphicSetAddresses.

Attribute applied when printing menu / HUD text.

Attribute byte currently selected by graphic layout opcode F2. Written into the display buffer with each tile; 00 means "use the attribute from the graphic data".

Sound index queued by Queue_Sound for Play_QueuedSound (00 = idle). Bit 07 marks a force-queue from Queue_Sound.

Camera-follow delay countdown.

Saved base address of the Berk script table while Start_Berk_Script walks a random entry. Written on entry to Start_Berk_Script and reloaded when a candidate row is rejected.

Pointer used by Drutt / trap door animation routines.

Entity type remembered while Drutt's trap door animation runs (Update_Drutt).

Secondary state byte for Drutt's trap door animation (Reset_Trap_Door_Animation_State / Update_Drutt).

Pointer used while updating miscellaneous entities.

Per-task dialogue pointers indexed by Update_Bad_Tempered_Thing_Dialogue_IndexTable. Task 00 skips this table and uses D7CD instead.

Current border colour and EAR bit. Written by Set_BorderSpeakerState; read by Play_QueuedSound before each speaker toggle.

Three-byte scratch written by game start and read by the pseudo-random routine.

Player control bits, written by Read_PlayerControls.

Bit	Meaning
00	Right
01	Left
02	Down (forward)
03	Up (back)
04	Fire (pick up / put down / interact)
05	Secondary fire / alternate action (keyboard T by default)
06	Pause (keyboard H by default; special-cased in Read_PlayerControls)
07	Unused

Pointer into Table_ControlKeyCodes used while redefine-keys walks the control table.

Non-zero to read Kempston (1F) in Read_PlayerControls; zero to use the keyboard table at Table_ControlKeyCodes.