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C2M

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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[edit]

Section header[edit]

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[edit]

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 [1])
NOTE Null-terminated string Plain text comments ([1])
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[edit]

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[edit]

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[edit]

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[edit]

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[edit]

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[edit]

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 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
0x11 Blue teleport
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)
0x44 Clone machine Modifier required, see below
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
0x4f Railroad track (Modifier required, see section below)
0x50 Steel wall
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 Inverter gate (N) Modifier allows other gates, see below
0x5d (Unused) Direction byte, Tile Specification for lower layer
0x5e Logic switch (ON)
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 (green) Modifier allows other styles, 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 (green) Modifier allows other styles, see below
0x71 Letter tile (space) 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 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
0x88 ON/OFF switch (OFF)
0x89 ON/OFF switch (ON)
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[edit]

The direction byte comes after enemy tiles and some others:

Value Meaning
0 North
1 East
2 South
3 West

Thin wall/Canopy bitmask[edit]

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[edit]

Any number of these bits can be combined:

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

Tile modifiers[edit]

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[edit]

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[edit]

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[edit]

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[edit]

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[edit]

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[edit]

This is an 8- or 16-bit modifier that affects the railroad track tile. The low-order 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 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) 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

REPL / PRPL section[edit]

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[edit]

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[edit]

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.
  1. 1.0 1.1 The NOTE section can contain multiple clues separated by a "[CLUE]" line. The clues are assigned to the clue tiles in reading order.