The Adventures of Captain Comic (DOS)

The Adventures of Captain Comic
Developer: Michael A. Denio Platform: DOS Released internationally: May 1, 1988 (revision 1); November 28, 1988 (revision 2); February 20, 1989 (revision 3); October 20, 1989 (revision 4); July 10, 1991 (revision 5) This game has unused code. This game has hidden developer credits. This game has unused graphics. This game has unused sounds. This game has unused text. This game has revisional differences. This game has a prerelease article This game has a notes page This game has a bugs page

The Adventures of Captain Comic is an EGA sidescroller.

You can play the game in a browser at the Internet Archive.

Sub-Pages

Prerelease Info

Notes

Bugs

Code Changes

Revisional Differences

The file COMIC.DOC describes five revisions of the game.

Revision 1 ( 5/01/88)

• Original Software Release.

Revision 2 (11/28/88)

• Added definable keyboard option.
• Keyboard definitions can be saved (KEYS.DEF) for future play.
• High score file (COMIC.HGH) by can be deleted to "clear" highscores.
• Several minor bug fixes.

Revision 3 ( 2/20/89)

• Revised player control. Jumping in cramped areas is now more consistent with the "feel" of jumping in open areas.
• Major bug fixes. This version contains no known bugs.

Revision 4 (10/20/89)

• Limited revisions. Added joystick feature to get feedback on the "feel" of the joystick control for use in future games.
  • Joystick option not yet available on PC XT class machines.

Revision 5 (7/10/91)

• Limited revisions again. Fixed the joystick to work with all PCs. I also modified the scoring system to remove 'bonus' points awarded when the player falls. This made beginner's score unnaturally high.

Revision 1 was reverse-engineered and modded into Prigodi Pìonerki Ksenì.

Maps

The map file format marks each tile as being either passable or solid. 6 of the 24 level maps changed their structure in a way that was not merely graphical. 5 of the 6 cases changed only once, in Revision 3. The remaining case, COMP2.PT, changed twice, in Revision 2 and Revision 3.

■ Revision 1 ■ Revision 2 ■ Revision 3

FOREST0.PT
Revision 3 shifted the platforms to make room for a bigger castle and extended the safety net under the first few jumps.
BASE2.PT
Revision 3 lengthened a platform by 1 tile.
SHED0.PT
Revision 3 moved around the 1-tile platforms and simplified the obstacle in the middle, making the use of the teleport wand to bypass it more intuitive. The shield moved from the left side to the right side of the obstacle.
SHED1.PT
Revision 3 changed a few platforms, notably enlarging the pit in the lower right, making it easier to teleport up to the item and door.
COMP0.PT
Revision 3 opened up a passage at the left side and simplified the obstacles in the middle of the stage.
COMP2.PT
In Revision 1, the gap to the right of the platform holding the lantern was 3 tiles wide, which is just possible to teleport across (from the right) if you start with one foot hanging off the edge. This made it possible to collect the lantern without traversing the SHED and COMP levels. Revision 2 prevented the sequence break by shortening the platform by 1 tile on the left. Revision 3 undid that change, but compensated by shortening the platform on the right by 1 tile.

Map Tiles

All levels except the castle saw changes to their map tiles. Not all map tiles are used, not even all of those that were newly redrawn in a revision.

LAKE.TT2
Revision 1	Revision 2	Revision 3	Revision 4	Revision 5
	Revision 2 redrew a cloud.	Revision 3 redrew the cloud again, and changed the look of some bricks.	Revision 4 added tiles for a castle on the far side of the lake, and rearranged other tiles to make room.	No changes in Revision 5.
FOREST.TT2
Revision 1	Revision 2	Revision 3	Revision 4	Revision 5
	Revision 2 dimmed some background stars.	Revision 3 reworked almost everything: castle walls, trees, and steps. The moon goes unused.	Revision 4 adds flowers and window borders, with other minor changes.	No changes in Revision 5.
SPACE.TT2
Revision 1	Revision 2	Revision 3	Revision 4	Revision 5
	Revision 2 changed some of the stars.	Revision 3 altered a planet and the galaxies.	Revisions 4 and 5 made no further changes.
BASE.TT2
Revision 1	Revision 2	Revision 3	Revision 4	Revision 5
In Revision 1, the door that leads back down to the planet is labeled "EARTH".	In Revision 2, it is labeled "TAMBI".		No changes in Revisions 4 and 5.
CAVE.TT2
Revision 1	Revision 2	Revision 3	Revision 4	Revision 5
	Revision 2 did not change any tiles.	Revision 3 slightly adjusted a background tile, and made doors look more like doors.	Revisions 4 and 5 made no further changes.
SHED.TT2
Revision 1	Revision 2	Revision 3	Revision 4	Revision 5
		Revision 3 redrew a cloud and changed an unused brick wall into a colored platform.	Revisions 4 and 5 made no further changes.
CASTLE.TT2
Revision 1	Revision 2	Revision 3	Revision 4	Revision 5
	The castle graphics did not change after Revision 1.
COMP.TT2
Revision 1	Revision 2	Revision 3	Revision 4	Revision 5
	Revision 2 did not change any tiles.	Revision 3 only changed a couple of platform end caps.	Revisions 4 and 5 made no further changes.

Graphics

In Revision 4, Comic traded his overalls (presumably a leftover from these sprites' not too subtle inspiration) for a V-neck more befitting a spaceman.

Revisions 1–3	Revisions 4–5

Fullscreen Graphics

The fullscreen graphics are stored in .EGA files. In Revision 1, the file format was just 32000 bytes of uncompressed EGA data. In Revision 2 and later revisions, the graphics are compressed with an RLE scheme.

SYS000.EGA
Revision 1	Revisions 2–4	Revision 5
	Revision 2 slightly shifted the text against the background starfield.	Revision 5 substantially reworked the lettering.

SYS001.EGA
Revision 1	Revisions 2–5
	Revision 2 slightly shifted the text against the background starfield.

SYS002.EGA
Revision 1	Revisions 2–5
	Revision 2 slightly shifted the text against the background starfield.

SYS003.EGA
Revisions 1–5
The interface graphic remained unchanged through all revisions, down to the copyright date.

SYS004.EGA
Revision 1	Revision 2	Revisions 3–5
	Revision 2 removed the shadow from text, and reordered and rearranged the items.	Revision 3 diminished the magnitude of a background star to make "Killer Bee" easier to read.

SYS005.EGA
Revision 1	Revisions 2–4	Revision 5
Revision 1 stores the high score screen inside the executable, not in a separate SYS005.EGA file. The graphic is the same as in Revisions 2–4.		Revision 5 replaced the background with character graphics.

Sound

To do: Identify the R5 title theme. Wikipedia claims it is "George Frideric Handel Harpsichord Suite In D Minor, HWV 428, Air" (here is the edit that added the claim), but that appears to be a conflation with the music of the NES port; and a misinterpretation of the cited paper by Gibbons (about the NES port), which says rather "Handel, Aria from Aria with Variations movement of Suite in D minor (no HWV)" (Table 1).

In Revisions 1–4, the main title theme, screen transition jingle, and game over sound were all riffs on the Marines' Hymn. These three sound effects changed to something else in Revision 5. Revision 5 omits a slow recapitulation of the title theme just before Captain Comic materializes. All other sound effects are the same in every revision.

	Revisions 1–4	Revision 5
Title
Game start		absent
Screen transition
Game over

Revision 5 is more in tune than earlier revisions. Captain Comic uses the PC speaker and so cannot set precise frequencies; it can only use frequencies of the form 1193182 / d, where d is a 16-bit integer. Revision 5 chooses d to get a close approximation of twelve-tone equal temperament, while earlier revisions only get close to the nearest integer frequency.

note	true frequency	R1–R4		R5
		divisor	frequency (error)	divisor	frequency (error)
C3	130.813 Hz	2394	131.004 Hz (+2.53 cents)	23a1	130.817 Hz (+0.06 cents)
D3	146.832 Hz	1fb5	146.998 Hz (+1.95 cents)	1fbe	146.835 Hz (+0.03 cents)
E3	164.814 Hz	1c3f	165.009 Hz (+2.05 cents)	1c48	164.804 Hz (−0.10 cents)
F3	174.614 Hz	1aa2	175.005 Hz (+3.87 cents)	1ab1	174.621 Hz (+0.06 cents)
G3	195.998 Hz	17c8	195.989 Hz (−0.08 cents)	17c8	195.989 Hz (−0.08 cents)
A3	220.000 Hz	1530	219.982 Hz (−0.14 cents)	1530	219.982 Hz (−0.14 cents)
B3	246.942 Hz	12df	246.984 Hz (+0.30 cents)	12e0	246.933 Hz (−0.06 cents)
C4	261.626 Hz	11ca	262.007 Hz (+2.53 cents)	11d1	261.605 Hz (−0.13 cents)
D4	293.665 Hz			0fdf	293.670 Hz (+0.03 cents)
E4	329.628 Hz			0e24	329.608 Hz (−0.10 cents)
F4	349.228 Hz			0d59	349.190 Hz (−0.19 cents)
F♯4	369.994 Hz			0c99	369.979 Hz (−0.07 cents)
G4	391.995 Hz			0be4	391.978 Hz (−0.08 cents)
A4	440.000 Hz			0a98	439.964 Hz (−0.14 cents)
B4	493.883 Hz	0974	493.050 Hz (−2.92 cents)	0974	493.050 Hz (−2.92 cents)
C5	523.251 Hz	08e9	523.096 Hz (−0.51 cents)	08e9	523.096 Hz (−0.51 cents)
D5	587.330 Hz	07f1	586.907 Hz (−1.25 cents)	07f1	586.907 Hz (−1.25 cents)
E5	659.255 Hz	0713	658.853 Hz (−1.06 cents)
F5	698.456 Hz	06ad	698.176 Hz (−0.70 cents)
G5	783.991 Hz	05f2	783.957 Hz (−0.08 cents)
A5	880.000 Hz	054b	880.577 Hz (+1.14 cents)

Code

Code Changes in Revision 2

Moves some variables to before the program entry point. The variables are preceded by a stub jmp main, which is unused because the EXE header already points at main.^ref

Adds a check that the game's custom interrupt handlers were properly installed. It does this by adding a special function to INT 3 (which otherwise controls the sound) to tweak a global variable. The game invokes INT 3 and checks that the global variable is tweaked as expected. However the failure branch of the check seems to be in error in this revision. Intead of exiting the program, it jump directly to the title screen, skipping the startup notice.^ref

Fleshes out the startup notice and pauses to let you read it.^ref

Adds a definable keymap and an interface for configuring it. The keymap is loaded from the file KEYS.DEF if present; otherwise it defaults to the Revision 1 keys.^ref

Fullscreen graphics are now RLE-compressed, and their loading moved into a subroutine instead of being inlined where needed.^ref Loads the high scores background from the FILE SYS005.EGA instead of storing it in the executable.^ref

Preserves the sound mute status through the landing sequence. In Revision 1, if you pressed F2 to mute the sound during the title, it would be unconditionally unmuted after awarding the player their initial stock of lives.^ref

Adds a check on the initial number of lives that leads to the unused instant-win mode.^ref

Removes a check for an unused −1 value of an internal sound-control variable.^ref

If the COMIC.HGH file cannot be opened, loads a default empty high scores table instead of terminating.^ref

Code Changes in Revision 3

The startup notice changes Revision 2 to Revision 3; Copyright 1988 to Copyright 1988, 1989; and begin. to begin.^ref

You can now press Esc to quit from the startup screen. Previously, Esc acted as an "any other key" to start the game.^ref

The code that reads a keypress during keyboard setup moves into a subroutine, which also clears the BIOS keyboard buffer after every input, instead of doing it once at the end. Disables interrupts in some, but not all, places where the BIOS keyboard buffer is cleared after reading a keypress.^ref

You can now map the Del key (scancode 53) during keyboard setup. In Revision 2, an off-by-one bug meant you could only map up to Ins (scancode 52).^ref

The interrupt handler for IRQ 1 (keyboard events) sets a global variable to the scancode of the most recent key event. In Revision 2, the variable represents the most recent key release, but in Revision 3, it represents the most recent key press.^ref You can see the difference easily in the keyboard setup menu by pressing and holding a key. In Revision 2, the key is not assigned until you release the key. In Revision 3, it is assigned as soon as you press it. The press/release change also allowed removing a hack that called the key-mapping subroutine once, before even showing the keyboard setup menu, simply to eat the K key event that would otherwise be immediately assigned to "Move Left".^ref You can see an artifact of this hack in Revision 2 using the fact that the key-mapping subroutine does not return until you have released a key that is not currently mapped to one of the game actions. At the startup screen, press and hold K. While it is being held, press and release another key. Any key will advance the screen except for those that are mapped by default (Left, Right, Space, Ins, Alt) and other keys that the key-mapping subroutine handles as special cases (Esc and any scancode above Ins). Caps Lock works to advance the screen, even though it is by default mapped to "Teleport", because the subroutine doesn't check that particular mapping. The keyboard-mapping subroutine has the side effect of printing "K       " to the screen, but it is not noticeable because the screen is cleared immediately after.

After being paused with Esc, the game no longer unpauses until Esc is released.^ref In Revision 2, holding Esc would cause the game to flicker paused and unpaused, and could get in an inverted state where pressing Esc would unpause and releasing it would pause.

Fixes the hover glitch. There is a variable (call it comic_jump_counter) that tracks the height of a player's jump. The variable is set to 4 (if you don't have the Boots) or 5 (if you do) whenever the player stands on solid ground, in preparation for a jump. comic_jump_counter counts down during every game tick that the player is jumping, and when it reaches 1, the player stops accelerating upward. In Revision 2, comic_jump_counter gets initialized to 0 when the player spawns at the start of the game or after dying. If you jump on the first possible frame, it skips past the sentinel value of 1 and underflows to ff, allowing you to keep the jump going for 255 ticks. Revision 3 fixes the bug by initializing comic_jump_counter to 4 instead.^ref The fix still leaves a minor bug: a first-frame jump will be as high as if you did not have the Boots, even if you do have them.

Jumps work differently under low ceilings. The following graphic compares identical jumps in Revision 2 (left) and Revision 3 (right). Formerly, Captain Comic couldn't jump at all in two-tile-high corridors; now, he can push a half a tile into the ceiling, just as in taller corridors. Comic also sticks to the ceiling longer, instead of quickly bouncing off.^ref The top of the screen is not considered an actual ceiling, and jumps that clip to the top of the screen haven't changed.

Code Changes in Revision 4

The startup notice changes Revision 3 to Revision 4, removes the promise to send registered users the question hotline phone number, changes the mailing address, and adds a prompt to press J to configure the joystick.^ref

Adds joystick play using the BIOS's native joystick support.^ref

Code Changes in Revision 5

Replaces the unused jmp main stub with an unused copyright notice.^ref

Makes the program exit if the game's custom interrupt handlers cannot be installed, instead of jumping to the title screen.^ref

The startup notice announces the availability of Captain Comic Episode II: Fractured Reality and registration details are moved to a separate screen. Inlines the display_xor_decrypt subroutine.^ref

Shifts the text in the keymap configuration one space to the left.^ref

Overhauls how joystick handling works. Installs a custom INT 21 handler to replace the BIOS's native joystick support.^ref Does a CPU speed test on startup to determine how many times to poll the joystick on each tick.^ref

Changes the joystick axis thresholds, seemingly with a bug in the left and up directions.^ref In Revision 4, the thresholds were 50% of the way between the zero and extreme values for left and right, and 75% of the way for up and down:

joystick_x_low  = 1/2 * joystick_x_zero + 1/2 * extreme_left
joystick_x_high = 1/2 * joystick_x_zero + 1/2 * extreme_right
joystick_y_low  = 1/4 * joystick_y_zero + 3/4 * extreme_up
joystick_y_high = 1/4 * joystick_y_zero + 3/4 * extreme_down

In Revision 5, the threshold is changed to 50% in the up and down directions, but also a sign is flipped in the left and up directions, making them no longer represent a weighted average of the zero and extreme values:

joystick_x_low  = 1/2 * joystick_x_zero - 1/2 * extreme_left
joystick_x_high = 1/2 * joystick_x_zero + 1/2 * extreme_right
joystick_y_low  = 1/2 * joystick_y_zero - 1/2 * extreme_up
joystick_y_high = 1/2 * joystick_y_zero + 1/2 * extreme_down

Joystick inputs now count as keypresses for the purpose of advancing through the title cards.^ref

Saves the video mode on startup and restores it on exit, instead of unconditionally restoring mode 2.^ref

Saves the es register in the wait_for_keypress subroutine.^ref

Reorders how the title sequence graphics are loaded and displayed.^ref

The time the title screen is displayed is increased from 10 ticks to 14 ticks.^ref

Clears the BIOS keyboard buffer in fewer places.^ref

Uses an auxiliary global variable to pass the size argument into the RLE decoding subroutine. Doubles the size of the RLE decoding buffer.^ref

Revises the double buffer handling to wait for vsync, and swap only the high byte of the video start offset pointer.^ref

No longer plays a recapitulation of the title music before beaming in.^ref

Zeroes Comic's health before respawning him and filling up his health again. In earlier revisions, the game would fill Comic's health and overcharge the health meter if it did not begin empty. This would award points, the same as if you had collected a Shield while at more than zero health.^ref

No longer decrypts and displays an empty string when exiting.^ref

Removes a block of unused bytes that may be an unused sound, and adds the unused strings sys006.ega and sys007.ega.^ref

Unused Map Tiles

LAKE.TT2
R1	R2	R3	R4	R5	Comments
FOREST.TT2
R1	R2	R3	R4	R5	Comments
					Revisions 1 and 2 had unused battlements with curved castle walls behind them. Later revisions changed the background to foliage and used one of the tiles. Revision 3 had tiles for a moon that remained unused. Revisions 4 and 5 changed the moon tiles into flowers and grass and used them.
SPACE.TT2
R1	R2	R3	R4	R5	Comments
					In Revisions 3 and later, the unused tile 38 depicting sparse stars is a duplicate of the used 00 and 47.
BASE.TT2
R1	R2	R3	R4	R5	Comments
					Stained wall tiles are present but unused in Revisions 1 and 2. They are used in later revisions.
CAVE.TT2
R1	R2	R3	R4	R5	Comments
					Unused cave tiles include a wooden bridge with rope handholds.
SHED.TT2
R1	R2	R3	R4	R5	Comments
					Revision 3 changed the unused white brick wall into a colored block and used it.
CASTLE.TT2
R1	R2	R3	R4	R5	Comments
COMP.TT2
R1	R2	R3	R4	R5	Comments

Unused Text

Unused in every revision: File error

The program simply terminates whenever it detects a file error and does not display this string.

Unused in Revision 1: sys005.ega

This would be the filename of the high scores graphic, but in Revision 1, the graphic is stored in the executable, not in a separate file.

Unused in Revision 5: sys006.ega, sys007.ega

These strings follow the naming convention of fullscreen graphics, but are never referenced.

Unused in Revision 5: \n\r\n\rCaptain Comic I - Planet of Death, Version SH1.0\n\rCopyright 1990 by Michael A. Denio\n\r

This string appears at offset 0000 in the executable, before the address where execution begins. It is never used or displayed. The year 1990 lies between the release dates of Revision 4 (October 20, 1989) and Revision 5 (July 10, 1991).

Revisions 2 and later display a copyright screen in text mode, before switching to graphics mode for the game. The text of the screen is XOR-obfuscated in the executable. Revision 1 also has such a screen, but the program doesn't wait for a keypress before entering graphics mode, so you never get to see it. Its unobfuscated contents are:

   The Adventures of Captain Comic\r\n
 Copyright (c) 1988 by Michael Denio\r\n

Unused Sound

In Revisions 1 through 4, there is a block of 24 unused bytes just after the title recapitulation sound effect. The unused bytes vaguely resemble a sound effect, except that they use a frequency divisor of 0001 instead of 0028 to indicate a rest. If it is a sound effect, this is what it would sound like. It's a 1193.182 Hz tone played three times.

Unused Graphics Masks

The icons at the bottom of the screen that indicate the number of lives remaining have transparency masks, but the subroutine that draws them does not use the masks, instead rendering them as fully opaque. The difference is imperceptible in the game, because the would-be transparent pixels are the same color as the background over which they are drawn.

Graphics with masks	Graphics without masks

Unused Instant-Win Mode

Just after counting up the player's initial stock of lives, the game checks whether the number of lives is exactly 4. If so, gameplay continues as normal; but if not, the game starts a timer to warp to the ending sequence after approximately 200 game ticks. It's the same timer that gets set after the player collects the last of the three treasures to win the game, but in that case, the timer is set to 20, not 200. There does not appear to be any way to change the initial number of lives short of hacking the game executable, so the code goes unused. The instant-win check is missing in Revision 1, but present in all later revisions.

Video of the effect in action in Revision 5.

; Disassembly of the relevant code in Revision 5. Starts at offset
; 0x4f0 in the unpacked executable (exclusive of the MZ header).
    2ea05e00    mov al, byte cs:[sound_is_enabled]
    50          push ax                 ; save sound mute status
    b80200      mov ax, SOUND_MUTE
    cc          int3                    ; call sound control subroutine
    b90500      mov cx, MAX_NUM_LIVES   ; loop 5 times
.loop:
    b80100      mov ax, 1
    e8c800      call wait_n_frames      ; wait 1 tick between each life awarded
    51          push cx                 ; gain_a_life uses cx
    e8291c      call gain_a_life
    59          pop cx
    e2f3        loop .loop

    b80300      mov ax, SOUND_STOP      ; stop the extra life sound that is playing but muted
    cc          int3
    58          pop ax
    2ea25e00    mov byte cs:[sound_is_enabled], al      ; restore the saved sound mute status

    b80300      mov ax, 3
    e8b200      call wait_n_frames      ; wait 3 ticks before subtracting the initial life
    e8571c      call lose_a_life

    803e460004  cmp byte [comic_num_lives], MAX_NUM_LIVES - 1   ; player has 4 lives?
    7405        je .num_lives_ok        ; always true
    c606fdd3c8  mov byte [win_timer], 200       ; win after 200 frames
.num_lives_ok:
    e9a205      jmp load_new_level

Unused F3 and F4 Keys

The F1 and F2 keys enable and disable sound. The game also checks F3 and F4, and even has variables devoted to tracking their state^ref, but does not use these two keys for anything. In Revision 1, it works somewhat differently, and there is a flat array tracking the state of all keys from LAlt (scancode 38) to Ins (scancode 52) inclusive, which encompasses many unused keys including F3–F10.