Holds the number of players and the chosen control method. Bit 0 is the player count, bits 1-2 are the control method.

Bits 1-2	Control Method
0	Keyboard
2	Kempston Joystick
4	Cursor Joystick

Bit 0 is reset for a 1UP game, or set for a 2UP game.

Holds a pointer to the currently used font data.

3-byte representation of the score.

Remaining 3-byte scores which follow High_Score. SetDefaults copies Default_High_Score over this whole table on initialisation.

Eight 3-letter names. SetDefaults copies Default_HallOfFame_Names here; HallOfFame prints them beside the scores at High_Score. The eighth name occupies HallOfFame_LastName.

Eighth name slot. InsertHighScore uses it as the LDDR source when opening a gap in the name table.

Byte after the name table. InsertHighScore uses it as the LDDR destination.

Updated each game loop by adding a ROM byte, addressed by the low byte of GameTimer, to itself.

Incremented once per game loop. The low byte indexes ROM when refreshing RandomNumber.

Start of the in-play object RAM that StartGame clears up to Laser_Parameter_1.

Has the frame been updated?

0	No
1	Yes

Holds a copy of the last FRAMES counter.

Working copy of the actor's cached Y position (*IX+11), compared with the new Y when a sprite is redrawn. LoadSpritePointers uses it to hold the high byte of the cached screen address instead.

Width in character columns of the sprite being drawn. ColouriseSprite uses it as the column count when colouring the sprite.

Height in pixel rows of the sprite being drawn, kept so ColouriseSprite can work out how many attribute rows to colour.

Rows of the new sprite image still to be drawn.

Rows of the old (cached) sprite image still to be erased. It is copied from *IX+10 and counted down while a sprite is redrawn.

Set to 1 by TestSpaceKey when SPACE is first pressed, so holding the key only counts once. Cleared again when SPACE is released.

Number of live aliens this frame. 33415 asks SpawnAlien to spawn another while this is less than 7.

3-byte representation of the score.

3-byte representation of the score.

Which player is currently active.

Value	Player
0	1UP
255	2UP

Attribute of the menu line currently being printed. MenuWriteText fetches it when printing a line.

At the beginning of each player turn there is a delay to allow the player to be ready for play.

Value	Game Mode
64	1UP
127	2UP

The larger delay for a 2UP game is useful for swapping players controls.

Set to 1 once a teleport has been set up. StartGame_ReadyStack then calls FinishTeleport to finish it with a debris burst, clearing the flag.

Number of explosion particles still moving. The debris handlers loop until this returns to 0.

Working Y used when filling explosion particles.

Non-zero while Jetman is dying, teleporting or otherwise not in play. Handlers return early and the game loop restarts at StartGame_ReadyStack.

Countdown used by the hall of fame input loop.

Current character position while entering a name.

Set after fire accepts a letter so the same press cannot advance again.

Which player's score is being ranked: 1 for 1UP, 2 for 2UP.

Non-zero while the other player's score still needs to be ranked after this insert.

Set to 1 when name entry starts for the first-ranked player and cleared by ReturnToRestart. Nothing reads it.

Insert flag for CompareHighScores. Non-zero (set from HighScore_Player) makes it also insert the score into the table; 0 only returns the rank.

Screen address where the letter being edited is printed. It advances by two columns after each letter is accepted.

Used when calculating the player's position in the high score table.

Three-letter name being entered. PrepareNameEntry seeds it as "AAA"; InsertHighScore copies it into the name table.

Working pitch. SoundsDebris plays three clicks from this byte; the debris handlers increment or decrement it.

Copy of GameOptions from the last menu pass, used to notice when the selection has changed.

Level of the active player. A value of 255 is treated as level 0 when Calculate_ActivePlayer_Level converts it to two digits. Swapped with InactivePlayer_Level by ChangePlayer.

Lives the active player has left. Swapped with InactivePlayer_Lives by ChangePlayer.

Bit 0 of the current level. FetchSprite and FetchActorSprite test it to decide whether to remap the sprite ID with MapSpriteBand.

0 when the rover is empty, 1 when an object is attached to it.

Level of the inactive player. A value of 255 is treated as level 0 when Calculate_InactivePlayer_Level converts it to two digits. Swapped with ActivePlayer_Level by ChangePlayer.

Lives the inactive player has left. Swapped with ActivePlayer_Lives by ChangePlayer.

Copy of LevelParity swapped in by ChangePlayer.

Copy of RoverCargoFlag swapped in by ChangePlayer.

Four 24-byte actor slots for the laser beams, in the same field order as Jetman_Slot. They are the first of the 24 actor slots, which run up to Actor_List_End. Every slot is laid out the same way:

Offset	Contents
0	Type (the sprite ID)
1	Screen column
2-3	World X
4	Y
5	Horizontal speed
6	Vertical thrust
7	Colour
8	Flags
9-15	Sprite cache, cleared by ClearSpriteCaches
16-23	State specific to the actor type

24-byte actor slot. InitialiseExplosion copies explosion templates here.

24-byte actor slot for Jetman. The last two bytes are the fuel pair at FuelLevel_1.

16-bit fuel remaining. InitialiseJetman initialises it to 36864.

24-byte actor slot for the moon rover.

Four 24-byte actor slots before Object_Slot_1. The fields follow the same order as Jetman_Slot. FillDebrisSlots fills debris from here.

Five 24-byte slots. ScanObjectSlots starts its scan here.

24-byte actor slot for the alien base, before the bomb slot. AlienBase_WorldX is its world X position and 24964 its Y position.

24-byte actor slot for the thrown bomb. Handler_Bombs copies the bomb template here when the slot is empty.

There are a maximum of 6 aliens on the screen at one time. Each slot is 24 bytes and uses the same field order as Jetman_Slot.

Byte	State	Byte	State	Byte	State
0	Type	8	Flags	16	Explode flag
1	Screen column	9	Pixel shift	17	Animation timer
2	World X (low)	10	Cached height	18	X wobble speed
3	World X (high)	11	Cached Y or width	19	X wobble
4	Y position	12	Graphic low	20	Y wobble speed
5	Horizontal speed	13	Graphic high	21	Y wobble
6	Vertical thrust	14	Screen low	22	Extra X speed
7	Colour	15	Screen high	23	Age

First address after the last actor slot, where object walks stop. It also starts the 0288 bytes where ChangePlayer stores the inactive player's actor slots.

Sixteen 5-byte particle records used by AnimateDebris.