C2M

Overview

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

Section header format

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 by CC2.
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 )
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, could be a MD5 hash of something
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 readonly 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.

A 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.

A 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
0x1	Floor
0x2	Wall
0x3	Ice
0x4	Ice, South West Corner
0x5	Ice, North West Corner
0x6	Ice, North East Corner
0x7	Ice, South East Corner
0x8	Water
0x9	Fire
0xa	Force Floor, North
0xb	Force Floor, East
0xc	Force Floor, South
0xd	Force Floor, West
0xe	Green Toggle Wall
0xf	Green Toggle Floor
0x10	Red Teleport
0x11	Blue Teleport
0x12	Yellow Teleport
0x13	Green Teleport
0x14	Exit
0x15	Slime (the obstacle)
0x16	Chip (the hero)	Direction byte, Tile Specification for tile underneath
0x17	Dirt Block	Direction byte, Tile Specification for tile underneath
0x18	Walker Enemy	Direction byte, Tile Specification for tile underneath
0x19	Ship Enemy	Direction byte, Tile Specification for tile underneath
0x1a	Ice Block	Direction byte, Tile Specification for tile underneath
0x1b	(Unused) East Panel	Tile Specification for tile underneath
0x1c	(Unused) South Panel	Tile Specification for tile underneath
0x1d	(Unused) South+East Panel	Tile Specification for tile underneath
0x1e	Gravel
0x1f	Door Toggle Button
0x20	Blue Tank Button
0x21	Blue Tank	Direction byte, Tile Specification for tile underneath
0x22	Red Door
0x23	Blue Door
0x24	Yellow Door
0x25	Green Door
0x26	Red Key	Tile Specification for tile underneath
0x27	Blue Key	Tile Specification for tile underneath
0x28	Yellow Key	Tile Specification for tile underneath
0x29	Green Key	Tile Specification for tile underneath
0x2a	IC Chip	Tile Specification for tile underneath
0x2b	Extra IC Chip	Tile Specification for tile underneath
0x2c	IC Chip Socket
0x2d	Push-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 tile underneath
0x34	Centipede	Direction byte, Tile Specification for tile underneath
0x35	Purple Ball	Direction byte, Tile Specification for tile underneath
0x36	Blob	Direction byte, Tile Specification for tile underneath
0x37	Red Teeth	Direction byte, Tile Specification for tile underneath
0x38	Fire box	Direction byte, Tile Specification for tile underneath
0x39	Clone Button
0x3a	Trap Button
0x3b	Cleats	Tile Specification for tile underneath
0x3c	Magno Shoes	Tile Specification for tile underneath
0x3d	Fire Shoes	Tile Specification for tile underneath
0x3e	Flippers	Tile Specification for tile underneath
0x3f	Red Thief
0x40	Red Bomb	Tile Specification for tile underneath
0x41	(Unused)
0x42	Trap
0x43	(Unused -- Behaves like Clone Machine)
0x44	Clone Machine (Modifier required, see below)
0x45	Clue Tile
0x46	Force Field, Random
0x47	Area Control Button
0x48	Revolving Door, South West
0x49	Revolving Door, North West
0x4a	Revolving Door, North East
0x4b	Revolving Door, South East
0x4c	Time Bonus	Tile Specification for tile underneath
0x4d	Time Toggle	Tile Specification for tile underneath
0x4e	Transformer
0x4f	Train Tracks Base (Modifier required, see section below)
0x50	Metal Wall
0x51	Time Bomb	Tile Specification for tile underneath
0x52	Helmet	Tile Specification for tile underneath
0x53	(Unused)	Direction byte, Tile Specification for tile underneath
0x54	(Unused)
0x55	(Unused)
0x56	Melinda	Direction byte, Tile Specification for tile underneath
0x57	Blue Teeth	Direction byte, Tile Specification for tile underneath
0x58	(Unused) Explosion Animation	Direction byte, Tile Specification for tile underneath
0x59	Hiking Shoes	Tile Specification for tile underneath
0x5a	Male Only Sign
0x5b	Female Only Sign
0x5c	Inverter Gate, North (Modifier allows other gates, see below)
0x5d	(Unused)	Direction byte, Tile Specification for tile underneath
0x5e	Logic Switch, On
0x5f	Flame Jet, Off
0x60	Flame Jet, On
0x61	Flame Jet Button
0x62	Lightning Bolt	Tile Specification for tile underneath
0x63	Yellow Tank	Direction byte, Tile Specification for tile underneath
0x64	Yellow Tank D-Pad
0x65	Mirror Chip (the enemy)	Direction byte, Tile Specification for tile underneath
0x66	Mirror Melinda	Direction byte, Tile Specification for tile underneath
0x67	(Unused)
0x68	Bowling Ball	Tile Specification for tile underneath
0x69	Rover	Direction byte, Tile Specification for tile underneath
0x6a	Time Penalty	Tile Specification for tile underneath
0x6b	Custom Floor, Brown (Modifier allows other styles, see below)
0x6c	(Unused)
0x6d	Panels/Canopy, see below	Panel/Canopy bitmask, Tile Specification for tile underneath
0x6e	(Unused)
0x6f	Railroad Crossing Sign	Tile Specification for tile underneath
0x70	Custom Wall, Brown (Modifier allows other styles, see below)
0x71	"Sunken" Floor (Modifier required, see below)
0x72	Purple Toggle Wall
0x73	Purple Toggle Floor
0x74	(Unused)
0x75	(Unused)
0x76	8-bit Modifier (see Modifier section below)	1 modifier byte, Tile Specification for affected tile
0x77	16-bit Modifier (see Modifier section below)	2 modifier bytes, Tile Specification for affected tile
0x78	32-bit Modifier (see Modifier section below)	4 modifier bytes, Tile Specification for affected tile
0x79	(Unused)	Direction byte, Tile Specification for tile underneath
0x7a	10 Point Flag	Tile Specification for tile underneath
0x7b	100 Point Flag	Tile Specification for tile underneath
0x7c	1000 Point Flag	Tile Specification for tile underneath
0x7d	Stay Up Green Wall
0x7e	Pop Down Green Wall
0x7f	"Forbidden" mark (modifies items/keys)	Tile Specification for tile underneath
0x80	2x Points Flag	Tile Specification for tile underneath
0x81	Directional Block	Direction byte, Directional Arrows Bitmask, Tile Specification for tile underneath
0x82	Floor Mimic	Direction byte, Tile Specification for tile underneath
0x83	Green Bomb	Tile Specification for tile underneath
0x84	Green IC Chip	Tile Specification for tile underneath
0x85	(Unused)	Tile Specification for tile underneath
0x86	(Unused)	Tile Specification for tile underneath
0x87	Reverse Logic Button
0x88	Off Switch, Off
0x89	On Switch, On
0x8a	Red Thief
0x8b	Ghost	Direction byte, Tile Specification for tile underneath
0x8c	Steel Foil	Tile Specification for tile underneath
0x8d	Turtle
0x8e	Eye	Tile Specification for tile underneath
0x8f	Bribe	Tile Specification for tile underneath
0x90	Speed Shoes	Tile Specification for tile underneath
0x91	(Unused)
0x92	Hook	Tile Specification for tile underneath

Direction Byte

The direction byte comes after enemy tiles and some others:

Value	Meaning
0	North
1	East
2	South
3	West

Panel/Canopy Bitmask

Any number of these bits can be combined:

Bitmask	Meaning
0x1	Panel, North
0x2	Panel, East
0x4	Panel, South
0x8	Panel, West
0x10	Canopy

Directional Arrows Bitmask

Any number of these bits can be combined:

Bitmask	Meaning
0x1	Arrow, North
0x2	Arrow, East
0x4	Arrow, South
0x8	Arrow, 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.

Wire Modifier

This is an 8-bit modifier that affects floors, metal walls, on/off switches, transformers, and blue/red fans (possibly more?). It adds wires to the tile it affects. Any number of these bits can be combined:

Bitmask	Meaning
0x1	Wire, North
0x2	Wire, East
0x4	Wire, South
0x8	Wire, West
0x10	Wire Tunnel, North
0x20	Wire Tunnel, East
0x40	Wire Tunnel, South
0x80	Wire Tunnel, West

ASCII Modifier

This is an 8-bit modifier that affects "sunken" floors 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 Characterr (' ' 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, North
0x2	Arrow, East
0x4	Arrow, South
0x8	Arrow, West

Custom Floor/Wall Modifier

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

Value	Meaning
0x1	Custom Wall/Floor, Pink
0x2	Custom Wall/Floor, Yellow
0x3	Custom Wall/Floor, Blue

Logic Modifier

This is an 8-bit modifier that affects an inverter gate by replacing it with another gate:

Values	Meaning
0x1 through 0x3	Inverter Gate East/South/West
0x4 through 0x7	And Gate North/East/South/West
0x8 through 0xb	Or Gate North/East/South/West
0xc through 0xf	Xor Gate North/East/South/West
0x10 through 0x13	Latch North/East/South/West, Clockwise Arrow
0x14 through 0x17	Nand Gate North/East/South/West
0x1e through 0x27	Counter Gate 0 through 9
0x40 through 0x43	Latch North/East/South/West, Counter Clockwise Arrow

Track Modifier

This is an 8- or 16-bit modifier that affects the train tracks base tile. The low-order byte specifies which tracks exist; any number of bits can be combined:

Bitmask	Meaning
0x1	Track, North East
0x2	Track, South East
0x4	Track, South West
0x8	Track, North West
0x10	Track, Horizontal
0x20	Track, Vertical
0x40	Track Switch

The high order byte is optional and specifies which track is the active one. If omitted, the North East track is the active one. For tiles with a track switch, the active track is the only one that can be used (the other are shown red).

Value	Meaning
(Omitted)	North East track is active
0x100	South East track is active
0x200	South West track is active
0x300	North West track is active
0x400	Horizontal track is active
0x500	Vertical track is active

REPL / PRPL section

This section contains the replay data. If this is a PRPL section, it must be unpacked first (see Section Packing).

The contents of this section are as follows:

Bytes	Content
1	Unknown (Usually 0)
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 passed since previous input change. 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.