C2M

A C2M file (having the extension .c2m) is the file format which Chip's Challenge 2 individual levels are stored in.

The file is a binary file consisting of several sections one after the other, terminated by the END section. Each section begins with a section header, which is followed by the section's data.

All data in the file is little-endian.

Format

Section header

Bytes	Content
4	Four character code identifying the section, see table below. Codes shorter than 4 characters (such as "END") are padded with spaces (making "END " in this case).
4	The length of the section's data

Section types

Section ID	Content Type	Content
CC2M	Null-terminated string	The file's version. The latest version is "7", but ranges from "3" to "7" in the levels supplied with CC2.
LOCK	Null-terminated string	Usually "Custom version for Chuck Sommerville", optional. Seems to be ignored
TITL	Null-terminated string	Level title
AUTH	Null-terminated string	Level author, optional
VERS	Null-terminated string	Version of the CC2 editor which created this level, optional
CLUE	Null-terminated string	Level clue (Only one allowed, but see below )
NOTE	Null-terminated string	Plain text comments ()
OPTN	See OPTN section table below	Various level options
MAP / PACK	See MAP section table below	The level's map. A MAP section is not packed, a PACK section is.
KEY	16 bytes	Unknown, seems not required
REPL / PRPL	See REPL section table below	Solution replay, optional. A REPL section is not packed; a PRPL section is.
RDNY	No content (length is 0)	The presence of this section makes the level read-only so it can't be edited in the level editor.
END	No content (length is 0)	Signifies end of file

OPTN section

The size of the section can differ between file versions (and even between files with the same file version). Data beyond the size of the section is not read. (E.g. if the section size is 3, only the time and the view are stored.)

Bytes	Content
2	Time
1	0 - 10x10 view, 1 - 9x9 view, 2 - split view
1	0 - no solution exists / solution not verified, 1 - a solution exists (in a REPL / PRPL section) and it works
1	0 - show map in editor, 1 - hide it
1	0 - map is editable, 1 - map is readonly
16	MD5 hash of the contents of the REPL section, or unpacked PRPL section.
1	"Hide Logic" option
1	"CC1 Boots" option
1	Blobs behavior: 0 - deterministic, 1 - 4 patterns, 2 - extra random

Section packing

The PACK and PRPL sections contain compressed versions of the MAP and REPL sections respectively. The compression scheme is as follows:

Bytes	Content
2	Number of bytes in the uncompressed list.
Varies	A sequence of blocks which can each be either a Data Block or a Back-Reference Block. The sequence continues until it covers all bytes in the uncompressed list.

Data block

When encountered during decompression, the data block's N bytes of data are added to the list..

Bytes	Content
1	The length of the data (N), must be between 0x00 to 0x7f (else, this is not a Data Block)
N	N bytes of data.

Back-reference block

When encountered during decompression, COUNT bytes are copied from position (CURRENT - OFFSET) in the list to position CURRENT in the list. (Where CURRENT is the current position in the list, while COUNT and OFFSET are defined below)

Note that COUNT can be larger than OFFSET, allowing arbitrary pattern repetition to be efficiently encoded.

Bytes	Content
1	0x80 + The number of items this block decodes to (COUNT). Must be between 0x80 to 0xff (else, this is not a Back-Reference Block)
1	The offset from the current position in the list (OFFSET)

MAP / PACK section

This section contains the map data. If this is a PACK section, it must be unpacked using the above compression scheme first. The contents of this section is as follows:

Bytes	Content
1	The level's width (W)
1	The level's height (H)
Varies	A sequence of tile specifications for each tile in the level, arranged in left-to-right, top-to-bottom order.

Tile specification

The tile specification consists of 1 or more bytes. The first byte is always the tile value, decoded as follows:

Value	Tile	Additional data, if any	Modifier
0x1	Floor		Wires
0x2	Wall
0x3	Ice
0x4	Ice corner (SW)
0x5	Ice corner (NW)
0x6	Ice corner (NE)
0x7	Ice corner (SE)
0x8	Water
0x9	Fire
0xa	Force floor (N)
0xb	Force floor (E)
0xc	Force floor (S)
0xd	Force floor (W)
0xe	Green toggle wall
0xf	Green toggle floor
0x10	Red teleport		Wires
0x11	Blue teleport		Wires
0x12	Yellow teleport
0x13	Green teleport
0x14	Exit
0x15	Slime
0x16	Chip (the hero)	Direction byte, Tile Specification for lower layer
0x17	Dirt block	Direction byte, Tile Specification for lower layer
0x18	Walker	Direction byte, Tile Specification for lower layer
0x19	Ship	Direction byte, Tile Specification for lower layer
0x1a	Ice block	Direction byte, Tile Specification for lower layer
0x1b	Thin wall (S) (used in CC1 levels)	Tile Specification for lower layer
0x1c	Thin wall (E) (used in CC1 levels)	Tile Specification for lower layer
0x1d	Thin wall (SE) (used in CC1 levels)	Tile Specification for lower layer
0x1e	Gravel
0x1f	Green button
0x20	Blue button
0x21	Blue tank	Direction byte, Tile Specification for lower layer
0x22	Red door
0x23	Blue door
0x24	Yellow door
0x25	Green door
0x26	Red key	Tile Specification for lower layer
0x27	Blue key	Tile Specification for lower layer
0x28	Yellow key	Tile Specification for lower layer
0x29	Green key	Tile Specification for lower layer
0x2a	IC Chip	Tile Specification for lower layer
0x2b	Extra IC Chip	Tile Specification for lower layer
0x2c	Chip socket
0x2d	Pop-up wall
0x2e	Appearing wall
0x2f	Invisible wall
0x30	Solid blue wall
0x31	False blue wall
0x32	Dirt
0x33	Ant	Direction byte, Tile Specification for lower layer
0x34	Centipede	Direction byte, Tile Specification for lower layer
0x35	Purple ball	Direction byte, Tile Specification for lower layer
0x36	Blob	Direction byte, Tile Specification for lower layer
0x37	Angry teeth	Direction byte, Tile Specification for lower layer
0x38	Fire box	Direction byte, Tile Specification for lower layer
0x39	Red button
0x3a	Brown button
0x3b	Cleats	Tile Specification for lower layer
0x3c	Suction boots	Tile Specification for lower layer
0x3d	Fire boots	Tile Specification for lower layer
0x3e	Flippers	Tile Specification for lower layer
0x3f	Tool thief
0x40	Cherry bomb	Tile Specification for lower layer
0x41	Open trap (unused in main levels)
0x42	Trap
0x43	Clone machine (used in CC1 levels)		Clone direction (?)
0x44	Clone machine		Clone direction
0x45	Clue
0x46	Force floor (random)
0x47	Gray button
0x48	Swivel door (SW)
0x49	Swivel door (NW)
0x4a	Swivel door (NE)
0x4b	Swivel door (SE)
0x4c	Time bonus	Tile Specification for lower layer
0x4d	Stopwatch	Tile Specification for lower layer
0x4e	Transmogrifier		Wires
0x4f	Railroad track		Tracks (see below)
0x50	Steel wall		Wires
0x51	Time bomb	Tile Specification for lower layer
0x52	Helmet	Tile Specification for lower layer
0x53	(Unused)	Direction byte, Tile Specification for lower layer
0x54	(Unused)
0x55	(Unused)
0x56	Melinda	Direction byte, Tile Specification for lower layer
0x57	Timid teeth	Direction byte, Tile Specification for lower layer
0x58	Explosion animation (unused in main levels)	Direction byte, Tile Specification for lower layer
0x59	Hiking boots	Tile Specification for lower layer
0x5a	Male-only sign
0x5b	Female-only sign
0x5c	Logic gate		Gate type and direction (see below)
0x5d	(Unused)	Direction byte, Tile Specification for lower layer
0x5e	Pink button		Wires
0x5f	Flame jet (OFF)
0x60	Flame jet (ON)
0x61	Orange button
0x62	Lightning bolt	Tile Specification for lower layer
0x63	Yellow tank	Direction byte, Tile Specification for lower layer
0x64	Yellow tank button
0x65	Mirror Chip	Direction byte, Tile Specification for lower layer
0x66	Mirror Melinda	Direction byte, Tile Specification for lower layer
0x67	(Unused)
0x68	Bowling ball	Tile Specification for lower layer
0x69	Rover	Direction byte, Tile Specification for lower layer
0x6a	Time penalty	Tile Specification for lower layer
0x6b	Custom floor		Style (see below)
0x6c	(Unused)
0x6d	Thin wall / Canopy	Panel/Canopy bitmask (see below), Tile Specification for lower layer
0x6e	(Unused)
0x6f	Railroad sign	Tile Specification for lower layer
0x70	Custom wall		Style (see below)
0x71	Letter tile (space)		Glyph type (see below)
0x72	Purple toggle floor
0x73	Purple toggle wall
0x74	(Unused)
0x75	(Unused)
0x76	8-bit Modifier (see Modifier section below)	1 modifier byte, Tile Specification for affected tile	N/A
0x77	16-bit Modifier (see Modifier section below)	2 modifier bytes, Tile Specification for affected tile	N/A
0x78	32-bit Modifier (see Modifier section below)	4 modifier bytes, Tile Specification for affected tile	N/A
0x79	(Unused)	Direction byte, Tile Specification for lower layer
0x7a	10 point flag	Tile Specification for lower layer
0x7b	100 point flag	Tile Specification for lower layer
0x7c	1000 point flag	Tile Specification for lower layer
0x7d	Solid green wall
0x7e	False green wall
0x7f	Not allowed marker	Modifies tools/keys. Tile Specification for lower layer
0x80	2x points flag	Tile Specification for lower layer
0x81	Directional block	Direction byte, Directional Arrows Bitmask, Tile Specification for lower layer
0x82	Floor mimic	Direction byte, Tile Specification for lower layer
0x83	Green bomb	Tile Specification for lower layer
0x84	Green chip	Tile Specification for lower layer
0x85	(Unused)	Tile Specification for lower layer
0x86	(Unused)	Tile Specification for lower layer
0x87	Black button		Wires
0x88	ON/OFF switch (OFF)		Wires
0x89	ON/OFF switch (ON)		Wires
0x8a	Key thief
0x8b	Ghost	Direction byte, Tile Specification for lower layer
0x8c	Steel foil	Tile Specification for lower layer
0x8d	Turtle
0x8e	Secret eye	Tile Specification for lower layer
0x8f	Thief bribe	Tile Specification for lower layer
0x90	Speed boots	Tile Specification for lower layer
0x91	(Unused)
0x92	Hook	Tile Specification for lower layer

Direction byte

The direction byte comes after enemy tiles and some others:

Value	Meaning
0	North
1	East
2	South
3	West

Thin wall/Canopy bitmask

Any number of these bits can be combined:

Bitmask	Meaning
0x1	Thin wall (N)
0x2	Thin wall (E)
0x4	Thin wall (S)
0x8	Thin wall (W)
0x10	Canopy

Directional block arrows bitmask

Any number of these bits can be combined:

Bitmask	Meaning
0x1	North
0x2	East
0x4	South
0x8	West

Tile modifiers

The modifier "tiles" (0x76, 0x77, 0x78) affect the tile specification that they carry in their additional data. The meaning of the modifier value depends on the type of tile they affect.

The size of the modifier is irrelevant, and modifiers default to zero. That is, if a tile is expecting a 16-bit modifier but the high byte is zero, an 8-bit modifier works as well. If a tile is expecting an 8-bit modifier which is zero, the modifier may be omitted entirely.

Wire modifier

This is an 8-bit modifier that affects floors, steel walls, ON/OFF switches, transmogrifiers, and blue and red teleports. It adds wires to the tile it affects. Any number of these bits can be combined:

Bitmask	Meaning
0x1	Wire (N)
0x2	Wire (E)
0x4	Wire (S)
0x8	Wire (W)
0x10	Wire tunnel (N)
0x20	Wire tunnel (E)
0x40	Wire tunnel (S)
0x80	Wire tunnel (W)

Letter tile modifier

This is an 8-bit modifier that affects letter tiles by adding a symbol (usually an ASCII symbol) to them:

Values	Meaning
0x1c	Up arrow
0x1d	Right arrow
0x1e	Down arrow
0x1f	Left arrow
0x20 through 0x5f	Corresponding ASCII character (' ' through '_')

Clone machine arrow modifier

This is an 8-bit modifier that affects clone machines by specifying their direction. The values can be combined and will show up on the clone machine appropriately, but the game will only clone in one direction.

Value	Meaning
0x1	Arrow (N)
0x2	Arrow (E)
0x4	Arrow (S)
0x8	Arrow (W)

Custom floor/wall modifier

This is an 8-bit modifier that affects custom walls or floors by replaces their style:

Value	Meaning
0x0	Green
0x1	Pink
0x2	Yellow
0x3	Blue

Logic modifier

This is an 8-bit modifier that affects an inverter gate by replacing it with another gate. Modifiers outside of the ranges specified below will produce voodoo tiles.

Most logic gates have 4 assigned values instead of just 1; unless otherwise specified below, the face direction of the logic gate is determined by its index, stored in the order: North, East, South, West.

Values	Meaning
0x0 through 0x3	Inverter gate
0x4 through 0x7	AND gate
0x8 through 0xb	OR gate
0xc through 0xf	XOR gate
0x10 through 0x13	Latch gate (clockwise arrow)
0x14 through 0x17	NAND gate
0x1e through 0x27	Counter gate (0 through 9)
0x40 through 0x43	Latch gate (counterclockwise arrow)

Track modifier

This is a 16-bit modifier that affects the railroad track tile. The low byte specifies which tracks exist; any number of bits can be combined:

Bitmask	Meaning
0x1	Turn (NE)
0x2	Turn (SE)
0x4	Turn (SW)
0x8	Turn (NW)
0x10	Horizontal
0x20	Vertical
0x40	Track switch

The high byte is comprised of two nybbles. The lower nybble specifies which track is active. For tiles with a track switch, the active track is the only one that can be used; the others are shown in red.

Value	Meaning
0x000	NE track is active
0x100	SE track is active
0x200	SW track is active
0x300	NW track is active
0x400	Horizontal track is active
0x500	Vertical track is active

The upper nybble is the tile's initial "entered" direction. When an actor starts the level already on top of this tile, it's treated as though it entered by moving in this direction. (If there are no tracks corresponding to that direction, the actor will be unable to move.)

REPL / PRPL section

This section contains the replay data. If this is a PRPL section, it must be unpacked first (see Section Packing). However the hash for the replay and the valid solution bit-flag is set in the OPTN section and not here

The contents of this section are as follows:

Bytes	Content
1	Usually 0; function unknown
1	Random force floor initial direction
1	Randomness seed (used by blobs)
Varies	A sequence of input changes; optionally terminated by 0xff

Input change

Specifies a change in input:

Bytes	Content
1	Number of frames to wait before inputting the new input. The last input is still held while the new input is pending. Always <= 0xfc. Larger delays are specified via multiple input changes
1	An input bitmask specifying the new input

Input bitmask

Specifies which keys are pressed, any number of bits can be combined:

Bitmask	Meaning
0x1	Drop item
0x2	Down
0x4	Left
0x8	Right
0x10	Up
0x20	Switch character
0x40	Cycle items
0x80	If set, this input is for player 2 in a split-screen game