Editing 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 ===
{| class="wikitable" border="1"
!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 ===
{| class="wikitable" border="1"
!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 <ref name=":0">The NOTE section can contain multiple clues separated by a "[CLUE]" line. The clues are assigned to the clue tiles in reading order.</ref>)
|-
|NOTE
|Null-terminated string
|Plain text comments (<ref name=":0" />)
|-
|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 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.)
{| class="wikitable" border="1"
!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:

{| class="wikitable" border="1"
!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..
{| class="wikitable" border="1"
!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.
{| class="wikitable" border="1"
!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:
{| class="wikitable" border="1"
!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:
{| class="wikitable" border="1"
!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 wall|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
|[[Glider|Ship]]
|Direction byte, Tile Specification for lower layer
|-
|0x1a
|[[Ice block]]
|Direction byte, Tile Specification for lower layer
|-
|0x1b
|[[Thin wall]] ''(E) (used in CC1 levels)''
|Tile Specification for lower layer
|-
|0x1c
|[[Thin wall]] ''(S) (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
|[[Tank|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
|[[Computer chip|IC Chip]]
|Tile Specification for lower layer
|-
|0x2b
|Extra [[Computer chip|IC Chip]]
|Tile Specification for lower layer
|-
|0x2c
|[[Socket|Chip socket]]
|
|-
|0x2d
|[[Recessed wall|Pop-up wall]]
|
|-
|0x2e
|[[Appearing wall]]
|
|-
|0x2f
|[[Invisible wall]]
|
|-
|0x30
|Solid [[blue wall]]
|
|-
|0x31
|False [[blue wall]]
|
|-
|0x32
|[[Dirt]]
|
|-
|0x33
|[[Bug|Ant]]
|Direction byte, Tile Specification for lower layer
|-
|0x34
|[[Paramecium|Centipede]]
|Direction byte, Tile Specification for lower layer
|-
|0x35
|[[Ball|Purple ball]]
|Direction byte, Tile Specification for lower layer
|-
|0x36
|[[Blob]]
|Direction byte, Tile Specification for lower layer
|-
|0x37
|[[Teeth|Angry teeth]]
|Direction byte, Tile Specification for lower layer
|-
|0x38
|[[Fireball|Fire box]]
|Direction byte, Tile Specification for lower layer
|-
|0x39
|[[Red button]]
|
|-
|0x3a
|[[Brown button]]
|
|-
|0x3b
|[[Ice skates|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
|[[Key thief]]
|
|-
|0x40
|[[Bomb|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
|[[Hint|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
|[[Teeth|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
|[[Gender-only sign|Male-only sign]]
|
|-
|0x5b
|[[Gender-only sign|Female-only sign]]
|
|-
|0x5c
|[[Inverter|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 tile|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 tile|Custom wall]] ''(green)''
|Modifier allows other styles, see below
|-
|0x71
|[[Letter tile]] ''(space)''
|Modifier required, see below
|-
|0x72
|[[Switch door|Purple toggle wall]]
|
|-
|0x73
|[[Switch door|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 [[Bonus flag|flag]]
|Tile Specification for lower layer
|-
|0x7b
|100 point [[Bonus flag|flag]]
|Tile Specification for lower layer
|-
|0x7c
|1000 point [[Bonus flag|flag]]
|Tile Specification for lower layer
|-
|0x7d
|Solid [[green wall]]
|
|-
|0x7e
|False [[green wall]]
|
|-
|0x7f
|[[No sign|Not allowed marker]]
|Modifies tools/keys. Tile Specification for lower layer
|-
|0x80
|2x points [[Bonus flag|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
|[[Switch|ON/OFF switch]] ''(OFF)''
|
|-
|0x89
|[[Switch|ON/OFF switch]] ''(ON)''
|
|-
|0x8a
|Tool [[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
|[[Bribe|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:
{| class="wikitable" border="1"
!Value
!Meaning
|-
|0
|North
|-
|1
|East
|-
|2
|South
|-
|3
|West
|}

==== Thin wall/Canopy bitmask ====
Any number of these bits can be combined:
{| class="wikitable" border="1"
!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:
{| class="wikitable" border="1"
!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.

==== Wire modifier ====
This is an 8-bit modifier that affects [[floor]]s, [[steel wall]]s, ON/OFF switches, [[transmogrifier]]s, and [[Blue teleport|blue]] and [[red teleport]]s<!--possibly more?-->. It adds [[wire]]s to the tile it affects. Any number of these bits can be combined:
{| class="wikitable" border="1"
!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 tile]]s by adding a symbol (usually an ASCII symbol) to them:
{| class="wikitable" border="1"
!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 machine]]s 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.
{| class="wikitable" border="1"
!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:
{| class="wikitable" border="1"
!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 tile]]s.

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.
{| class="wikitable" border="1"
!Values
!Meaning
|-
|0x0 through 0x3
|[[Inverter|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|Counter gate]] ''(0 through 9)''
|-
|0x40 through 0x43
|[[Latch gate]] ''(counterclockwise arrow)''
|}

==== Track modifier ====
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:
{| class="wikitable" border="1"
!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).
{| class="wikitable" border="1"
!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 ===
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:
{| class="wikitable" border="1"
!Bytes
!Content
|-
|1
|Usually 0; function unknown
|-
|1
|[[Force floor|Random force floor]] initial direction
|-
|1
|Randomness seed ''(used by [[blob]]s)''
|-
|Varies
|A sequence of input changes; optionally terminated by 0xff
|}

==== Input change ====
Specifies a change in input:
{| class="wikitable" border="1"
!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:
{| class="wikitable" border="1"
!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. <!-- doesn't work? -->
|}

<references/>

[[Category:Terminology]]
[[Category:File formats]]