Felix the Cat

On this page

How it plays
The edge-of-screen exit
Boss rooms
Randil’s run, stage by stage
Related
Mechanics
References
Sources

The atlas reads Felix the Cat’s US NES release in the ROM, which it disassembled with da65, and measures it in headless Mesen and FCEUX. Its reference run is Randil’s, TASVideos’ current publication for the game, 22:29.01 long¹. The addresses in the claims are the atlas’s reading.

#How it plays

Felix walks right into a stage that scrolls with him. Holding Right in the first stage, his speed grows by 48²/256 px a frame each frame to a top speed of 533²/256 px a frame². Falling, he gains 45³/256 px a frame of speed each frame, up to 6 px a frame³. Walking right, the camera settles with him 136⁴ px behind its scroll value, left of the screen’s middle⁴.

A stage ends at a line in it, not at the screen’s edge. Each frame the game compares Felix’s x with the stage’s bound, and once he is 290⁵ px past it the clear flag goes up. The first stage’s bound is x 3848^5,5. The camera stops 248⁴ px past the bound, so the line lies off the screen’s right edge⁴.

A three-digit timer drops by 1 every 60 frames while Felix is in a stage’s main area⁶. After a clear, the game counts the timer down a unit a frame, and the next stage starts 162⁷ frames after that count; Felix’s remaining power is counted first⁷. Felix’s power level runs from 0 to 3, and while it’s above 0 a count of 10 units drops one every 300 frames⁸. A hit above power level 0 takes a level away. At power 0, walking into the first stage’s first enemy costs a life, and the stage restarts from its start⁹.

#The edge-of-screen exit

Dragon Co.’s unlicensed Felix the Cat, a different game, ends a level when the player gets close to the screen’s right edge. KAGE-008 built a TASVideos submission around it, and the judge, Maru, reported a test file that saves 855 frames¹⁰ in level 1¹⁰.

Hudson’s exit test reads Felix’s x and the stage’s bound, never the scroll. Moved to 6 px below the scroll value¹¹ early in the first stage, near the screen’s right edge, Felix doesn’t clear the stage, and the camera catches up with him the next frame¹¹.

#Boss rooms

Each world ends in a boss room, and the exit test runs there too. A boss room’s bound is 0, so its stage ends once Felix’s x reaches 290⁵. The test never asks about the boss: placed at that x with the boss still up, Felix clears the stage, and the next one loads¹².

The line lies inside a wall. From x 224 on, each boss room’s map is solid from top to bottom, and Felix stops at x 215^13,13. Each frame, after he moves, the game reads the map 8 px ahead of him at three heights, and where a tile blocks, it takes the move back¹⁴. Above the screen and below it, the map reads its top and bottom rows, so neither a jump nor a fall goes around¹⁵.

Getting into the wall takes a single step of more than 24 px, and Felix’s top speed is about 2 px a frame. A moving platform’s push survives the test, but in Randil’s run none came in a boss room¹⁶. The door Felix enters World 2’s boss room by leads back into the same room¹⁷, and only the boss’s defeat moves the fight on¹⁸. In Randil’s run the seven fights take 4,982 frames in all, from the first frame of play to the boss’s defeat¹⁹.

#Randil’s run, stage by stage

Replayed in FCEUX, Randil’s movie passes 23 stages in 9 worlds²⁰. The table gives the frame play starts in each stage and the frame its clear flag goes up.

World	Stage index	Play starts	Clear
1²⁰	0	295²⁰	2265²⁰
1²⁰	1	2722²⁰	4674²⁰
1²⁰	2	5131²⁰	8076²⁰
2²⁰	3	8578²⁰	10,750²⁰
2²⁰	4	11,294²⁰	13,091²⁰
2²⁰	5	13,555²⁰	16,441²⁰
3²⁰	6	17,002²⁰	18,845²⁰
3²⁰	7	19,309²⁰	21,099²⁰
3²⁰	8	21,564²⁰	25,618²⁰
4²⁰	9	26,112²⁰	28,080²⁰
4²⁰	10	28,541²⁰	32,473²⁰
4²⁰	11	32,951²⁰	36,691²⁰
5²⁰	12	37,291²⁰	38,863²⁰
5²⁰	13	39,333²⁰	43,313²⁰
5²⁰	14	43,822²⁰	46,912²⁰
6²⁰	15	47,421²⁰	51,372²⁰
6²⁰	16	51,848²⁰	55,748²⁰
7²⁰	17	56,296²⁰	60,244²⁰
7²⁰	18	60,720²⁰	64,311²⁰
8²⁰	19	64,861²⁰	72,761²⁰
9²⁰	20	73,172²⁰	75,142²⁰
9²⁰	21	75,601²⁰	77,574²⁰
9²⁰	22	78,104²⁰	movie ends, 81,074²⁰

Mechanics

Mechanic	Kind	How
Level end		a stage ends when Felix's x passes the stage's bound plus 290, a line in the stage rather than on the screen
Scrolling	Follow	walking right, the camera keeps Felix 136 px behind its scroll value and stops 248 px past the stage's bound
Time limit	Per level	a three-digit timer drops every 60 frames, and the clear counts what's left
Power-up		a power level from 0 to 3 whose 10 units count down every 300 frames
Lives	Restart point	in the first stage, a lost life restarts it from its start
Boss fight		each boss room runs the same exit test, from a bound of 0, behind a wall solid from top to bottom
Tile collision		a 512 px ring of 16 px tiles; a blocked step is taken back, but a platform's push isn't
Running		the x speed builds by a step from RAM to a cap of 533/256 px a frame
Gravity		45/256 px a frame per frame, to 6 px a frame
Object slots		Felix is slot 0 of tables of 22

Every claim about this game, by concept (23)

general	Felix's push `$041D` comes from one routine, in PRG bank 12: a platform whose x swings with the frame counter sets it, while Felix rides, to the change in its x that frame, and the object pass clears it again afterward. The mover adds it to Felix's x, and the wall test never takes it back (felix-the-cat/wall-test). In FCEUX's replay of the 1625M movie the push was 1 px either way, and it came only in the main areas of stage indices 1, 2, 7, 9, 10, 12, 18, and 22, never in a boss room.	Code
general	TASVideos' current Felix the Cat (USA) publication, 1625, is Randil's 22:29.01 run from 2010, made in FCEU 0.98.28 and tagged "Takes intentional damage".	Web
Boss fight	The exit test has no boss condition. Each of the seven boss rooms, stage indices 2, 5, 8, 11, 14, 16, and 18, has a bound of 0, so it ends at x 290, inside the room's wall (felix-the-cat/boss-wall). In Mesen, from power-on, with each boss stage cleared at its bound and `$040C` set to 3 where the stage's last door would set it, the game's room change loads the boss room; Felix placed there at x 290 with the boss up sets the clear flag the next frame, the fight's step `$0411` still at 0, and the next stage loads.	Verified
	In each of the seven boss rooms, the map's columns 14 to 31, x 224 to 511 of its 512 px, are solid from top to bottom, and so is column 0. The wall test (felix-the-cat/wall-test) stops Felix at x 215, where the point 8 px ahead of him reaches the wall. In Mesen, moving right at his top speed of 533/256 px a frame from x 215, he stays at 215 at every height, from above the map to below it.	Verified
	`$0411` is a boss stage's step: 0 in the fight, 1 once the boss is beaten, and 2 in the room after. Only two instructions add to it: `$A20D` in PRG bank 13, in the routine that runs when the boss is beaten, and `$FA13`, in the room change that `$040C` = 3 asks for. A door asks for it only in a main area (felix-the-cat/boss-room-door); in the boss room, bank 13's `$A1B9` stores the 3. Every store to `$0411` writes 0, or `$FF` that `$FA13` lifts to 0 at once. In FCEUX's replay of the 1625M movie, in World 1, the step went from 0 to 1 at `$A20D` on frame 7,643; on frame 7,880 `$A1B9` set `$040C` to 3, and `$FA13` took the step to 2.	Code
	A door in a boss room leads back into the same room. Pressing Down on a door tile sends Felix down it, and the door's kind picks the room change. In a boss room (`$040D` = 8), `$CABF` gives every door kind 2 except in stage index 22, and kind 2 is a hop back up where he went down. Only kind 3 moves the boss step on (felix-the-cat/boss-step), and `$CB90` gives it only to a door in a main area, with the step at 0. Stage index 5's boss room has a door tile where Felix comes in. In FCEUX, Down on it during the fight sends him down and back up at x 48, with the fight still on.	Code
	In Randil's 1625M movie, replayed in FCEUX, the seven boss fights last 627 to 733 frames from the first frame of play in the boss room to the frame the boss is beaten (`$0411` reaches 1), 4,982 frames in all.	Our research
Gravity	Falling, with `$0616` below 3 and `$03B1` clear, Felix's y speed grows by 45 (in 1/256 px, down positive) each frame up to a cap of 1,536, 6 px a frame, as measured at the first stage's start.	Verified
Level end	`$33` is the stage index. A stage ends at `$FA20`, which adds 1 to it once the clear flag (`$03B7`) is up and the tally has run the timer down to 000. In the 1625M replay it reads 0 in the first stage and counts up to 22 in the last.	Code
	Three instructions in the ROM store to the clear flag `$03B7`. The stage load clears it; the exit test in the fixed bank sets it from Felix's x (felix-the-cat/exit-threshold); and a routine in PRG bank 12 sets it when a countdown at `$042B` reaches 0.	Code
	Every frame of play until the clear flag `$03B7` is up, the game subtracts `$32` and the stage's bound (`$BB:$BD`) from Felix's x and sets the flag when the result is at least `$F0`. A stage ends when Felix's x reaches its bound plus 290; in the first stage, whose bound is 3,848, that's x 4,138.	Verified
	The fixed bank's exit test reads Felix's x and the stage's bound, never the scroll. For example, walked a second into the first stage and placed 6 px below the scroll value, near the right edge of the screen, Felix doesn't clear the stage: the camera re-centers on him the next frame, and the clear flag stays at 0.	Verified
	KAGE-008's rejected TASVideos submission 6487 plays Dragon Co.'s unlicensed Felix the Cat, a different game from Hudson's, and ends levels "if the player is close to go off-screen to the right". The judge, Maru, adds that the player only has to jump "as much as possible to get to the right of the screen" and reports a test file saving 855 frames in level 1.	Web
	Replayed in FCEUX, Randil's 1625M movie passes 23 stages in 9 worlds of 3, 3, 3, 3, 3, 2, 2, 1, and 3 stages. For each stage the table gives the frame play starts (game mode `$28` reaches 5) and the frame the clear flag goes up; the last stage runs to the movie's end at frame 81,074.	Our research
Lives	A hit at power level 0 (`$03C6`) sets `$03CD` to `$FF` and Felix's y speed to `$F7:00`, upward; above 0, it sets `$03CD` to `$B4` and takes 1 from the power level instead. Walking right from the start of the first stage at power 0, the Mesen probe sees Felix hit at x 281, the lives digits (`$03A5`-`$03A6`) lose 1, and the stage restart with Felix at x 48.	Verified
Object slots	The atlas reads Felix as slot 0 of the game's object tables, and the tables as 22 slots each from the 22-byte spacing of the x and y tables. His x in the stage is `$0658:$0642` with a fraction byte at `$062C`, and his y is `$069A:$0684` with a fraction at `$066E`, growing downward. His x speed is `$06C6:$06B0` and his y speed `$06F2:$06DC`, signed, in 1/256 px a frame; each frame the mover adds the x speed, plus a signed byte at `$041D`, to the x.	Code
Power-up	`$03C6` holds Felix's power level, 0 to 3 in the 1625M run. While it's above 0, `$03C0` counts down one unit every 300 frames (150 odd frames, counted at `$03C1`); each change of level in the run that left it above 0 set `$03C0` back to 10.	Code
Running	Holding Right from a standstill in the first stage at power level 0, with `$0616` below 3, Felix's x speed grows by a step read from `$03B3`, 48 (in 1/256 px) there, each frame up to the cap of 533, about 2.08 px a frame, which it reaches on the twelfth frame.	Verified
Scrolling	The playfield's scroll is `$16:$14`, which the raster split writes to `$2005`. In the Mesen probe, Felix's screen x is about x − scroll + 256: walking right, the camera settles with his x 136 px below the scroll value, and a sprite of his covers screen x 120. The scroll stops at the stage's bound plus 248.	Verified
Tile collision	Each frame of play, after the mover adds Felix's x speed and push to his x, the fixed bank's `$D05F` checks him against the screen's edges or the map. With his x's high byte past the bound's, or equal to it with a low byte of `$DB` or more outside a boss fight (and a few other cases), the game walks him right (the auto-walk) and tests the map. Short of that, an x less than 8 or at least 240 past `$B7:$B9` sets his x speed to 1 px a frame back inward, and the map isn't read that frame. Otherwise, moving right, it reads the map 8 px ahead of him, normally at y + 1, y − 8, and y + 13 (moving left, 8 px behind), and if a tile there blocks, it subtracts that frame's x speed from his x again. Then `$D191` moves x 1 px toward 7 or 8 px into its 16 px column.	Code
Tile collision	The map that Felix's tile tests read is 32 columns of 16 px by 24 rows of 16 px in cartridge RAM at `$6000`-`$63FF`, a ring that repeats every 512 px of x. A tile's type is the low nibble of its entry in a table at `($CA)`. Types 1, 14, and 15 block both ways; type 4 blocks only moving left, and type 5 only moving right. A point above the map reads the top row, and one 384 px down or more reads the bottom row, where any nonzero type counts as 1.	Code
Time limit	Once the clear flag is up, the game counts the timer down one unit a frame, and the stage index moves on 162 frames after the timer's count, so the wait after a clear is the timer's reading plus 162 frames. With the power level above 0, the power's remaining units (`$03C0`) are counted first, about 15 frames each.	Verified
Time limit	The timer is three digit tiles at `$03A9`-`$03AB` (tile `$10` is 0). During play in a stage's main area (`$0411` = 0) it drops by 1 every 60 frames, counted at `$03AC`, and at 000 without a clear the game sets `$03FA`, time over.	Code

References

^TASVideos' current Felix the Cat (USA) publication, 1625, is Randil's 22:29.01 run from 2010, made in FCEU 0.98.28 and tagged "Takes intentional damage".WebTASVideos publication 1625
How we know
NES Felix the Cat by Randil in 22:29.01 … Tags: Takes intentional damage … Emulator Replay: FCEU 0.98.28
publication page · archived copy ↗
Checked against the evidence by its author, an AI model, 2026-10-25.
Checked by a second AI model, 2026-10-25.
In the claim ledger
^ a b cHolding Right from a standstill in the first stage at power level 0, with $0616 below 3, Felix's x speed grows by a step read from $03B3, 48 (in 1/256 px) there, each frame up to the cap of 533, about 2.08 px a frame, which it reaches on the twelfth frame.Verified“Felix the Cat (USA)”revised
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $D68E-$D701: add $03B3 to the x speed (or $03B4, when the x speed is below $0421:$0420); with $0616,X below 3, cap it at $0215; with 3 or more, at $01AA unless $03BF is 7. We don't reproduce the bytes.
Measured by a script in MesenCE 2.2.1 (build 4b8a196), on Felix the Cat (USA) (SHA-1 b57b1c6e6933…). It fails if the result disagrees with the claim.
The numbers come from the run; its author, an AI model, checked the script measures what the claim says, 2026-10-25.
Revised after a check by a second AI model, 2026-10-25.
In the claim ledger
^ a bFalling, with $0616 below 3 and $03B1 clear, Felix's y speed grows by 45 (in 1/256 px, down positive) each frame up to a cap of 1,536, 6 px a frame, as measured at the first stage's start.Verified“Felix the Cat (USA)”revised
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $D702-$D72C: unless $03B1 is set, and with $0616,X below 3, call $8917 with A = $2D and $3C = 6; bank 12 $8917-$8936 (mapped at $8000): add A to $06F2:$06DC; if the result isn't negative and its high byte is at least $3C, set it to $3C:00. We don't reproduce the bytes.
Measured by a script in MesenCE 2.2.1 (build 4b8a196), on Felix the Cat (USA) (SHA-1 b57b1c6e6933…). It fails if the result disagrees with the claim.
The numbers come from the run; its author, an AI model, checked the script measures what the claim says, 2026-10-25.
Revised after a check by a second AI model, 2026-10-25.
In the claim ledger
^ a b c dThe playfield's scroll is $16:$14, which the raster split writes to $2005. In the Mesen probe, Felix's screen x is about x − scroll + 256: walking right, the camera settles with his x 136 px below the scroll value, and a sprite of his covers screen x 120. The scroll stops at the stage's bound plus 248.Verified“Felix the Cat (USA)”revised
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $C1FC-$C224, the raster split: for split $2A, $16,X and $1A,X bit 0 pick the nametable, then $14,X and $18,X go to $2005 as the X and Y scroll. We don't reproduce the bytes.
Measured by a script in MesenCE 2.2.1 (build 4b8a196), on Felix the Cat (USA) (SHA-1 b57b1c6e6933…). It fails if the result disagrees with the claim.
The numbers come from the run; its author, an AI model, checked the script measures what the claim says, 2026-10-25.
Revised after a check by a second AI model, 2026-10-25.
In the claim ledger
^ a b c dEvery frame of play until the clear flag $03B7 is up, the game subtracts $32 and the stage's bound ($BB:$BD) from Felix's x and sets the flag when the result is at least $F0. A stage ends when Felix's x reaches its bound plus 290; in the first stage, whose bound is 3,848, that's x 4,138.Verified“Felix the Cat (USA)”
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $F7FF-$F840: with $03B7 at 0, ($0658:$0642 - $32) - $BB:$BD to $09:$08; if $09:$08 - $F0 isn't negative, set $03B7 to 1 and start two sounds. We don't reproduce the bytes.
Measured by a script in MesenCE 2.2.1 (build 4b8a196), on Felix the Cat (USA) (SHA-1 b57b1c6e6933…). It fails if the result disagrees with the claim.
The numbers come from the run; its author, an AI model, checked the script measures what the claim says, 2026-10-25.
Checked by a second AI model, 2026-10-25.
In the claim ledger
^The timer is three digit tiles at $03A9-$03AB (tile $10 is 0). During play in a stage's main area ($0411 = 0) it drops by 1 every 60 frames, counted at $03AC, and at 000 without a clear the game sets $03FA, time over.Code“Felix the Cat (USA)”
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $F7B2-$F7FC: skip unless $0411 is 0; INC $03AC; below $3C stop; else reset it and take 1 from $03AB, borrowing from $03AA and $03A9; fixed bank $F934-$F947: at 000 with $03B7 clear and $0411 at 0, $03FA = 1. We don't reproduce the bytes.
Checked against the evidence by its author, an AI model, 2026-10-25.
Checked by a second AI model, 2026-10-25.
In the claim ledger
^ a bOnce the clear flag is up, the game counts the timer down one unit a frame, and the stage index moves on 162 frames after the timer's count, so the wait after a clear is the timer's reading plus 162 frames. With the power level above 0, the power's remaining units ($03C0) are counted first, about 15 frames each.Verified“Felix the Cat (USA)” · 1625M, replayed in FCEUX
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $F707-$F761: with $03B7 set and $03C6 and $03C0 above 0, step $03C1 down; at 0, add to the score, reload it with 15, and take 1 from $03C0; otherwise add to the score and go on to the timer; fixed bank $F7B2-$F7FC: in play, count $03AC to $3C before the timer step; the tally enters at $F7C6, the step itself, which takes 1 from the three digits with borrows. We don't reproduce the bytes.
the 22 clears
Measured by a script in MesenCE 2.2.1 (build 4b8a196), on Felix the Cat (USA) (SHA-1 b57b1c6e6933…). It fails if the result disagrees with the claim.
The numbers come from the run; its author, an AI model, checked the script measures what the claim says, 2026-10-25.
Checked by a second AI model, 2026-10-25.
In the claim ledger
^$03C6 holds Felix's power level, 0 to 3 in the 1625M run. While it's above 0, $03C0 counts down one unit every 300 frames (150 odd frames, counted at $03C1); each change of level in the run that left it above 0 set $03C0 back to 10.Code“Felix the Cat (USA)” · 1625M, replayed in FCEUX
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $F787-$F7B0: with $03C6 above 0, on odd frames ($37 bit 0), DEC $03C1; at 0, reload $96 and DEC $03C0, floored at 0. We don't reproduce the bytes.
every change of $03C6
Checked against the evidence by its author, an AI model, 2026-10-25.
Checked by a second AI model, 2026-10-25.
In the claim ledger
^A hit at power level 0 ($03C6) sets $03CD to $FF and Felix's y speed to $F7:00, upward; above 0, it sets $03CD to $B4 and takes 1 from the power level instead. Walking right from the start of the first stage at power 0, the Mesen probe sees Felix hit at x 281, the lives digits ($03A5-$03A6) lose 1, and the stage restart with Felix at x 48.Verified“Felix the Cat (USA)”revised
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $F98E-$F9E9: take 1 from the two lives digits $03A5-$03A6 with a borrow; when they run out, set $33 to $18; fixed bank $CCE2-$CD23: if $03C5 is 4 or $03C6 is 0, $03CD = $FF, $0616,X = $0F, $06F2:$06DC = $F7:00; otherwise go to $CD24; fixed bank $CD24-$CD3B: $03CD = $B4, then DEC $03C6. We don't reproduce the bytes.
Measured by a script in MesenCE 2.2.1 (build 4b8a196), on Felix the Cat (USA) (SHA-1 b57b1c6e6933…). It fails if the result disagrees with the claim.
The numbers come from the run; its author, an AI model, checked the script measures what the claim says, 2026-10-25.
Revised after a check by a second AI model, 2026-10-25.
In the claim ledger
^ a bKAGE-008's rejected TASVideos submission 6487 plays Dragon Co.'s unlicensed Felix the Cat, a different game from Hudson's, and ends levels "if the player is close to go off-screen to the right". The judge, Maru, adds that the player only has to jump "as much as possible to get to the right of the screen" and reports a test file saving 855 frames in level 1.WebTASVideos submission 6487
How we know
This method implies exploiting a glitch where if the player is close to go off-screen to the right, it'll autofinish the level. … While both are based on 'Felix the Cat' cartoon, both versions are completely different each other.
submission text · archived copy ↗
For reference, you just need to jump as much as possible to get to the right of the screen. I have a test file that saves 855 frames in level 1.
judge's note · archived copy ↗
Checked against the evidence by its author, an AI model, 2026-10-25.
Checked by a second AI model, 2026-10-25.
In the claim ledger
^ a bThe fixed bank's exit test reads Felix's x and the stage's bound, never the scroll. For example, walked a second into the first stage and placed 6 px below the scroll value, near the right edge of the screen, Felix doesn't clear the stage: the camera re-centers on him the next frame, and the clear flag stays at 0.Verified“Felix the Cat (USA)”revised
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $F7FF-$F840: the exit test reads Felix's x and the stage's bound, not the scroll ($14, $16). We don't reproduce the bytes.
Measured by a script in MesenCE 2.2.1 (build 4b8a196), on Felix the Cat (USA) (SHA-1 b57b1c6e6933…). It fails if the result disagrees with the claim.
The numbers come from the run; its author, an AI model, checked the script measures what the claim says, 2026-10-25.
Revised after a check by a second AI model, 2026-10-25.
In the claim ledger
^The exit test has no boss condition. Each of the seven boss rooms, stage indices 2, 5, 8, 11, 14, 16, and 18, has a bound of 0, so it ends at x 290, inside the room's wall (felix-the-cat/boss-wall). In Mesen, from power-on, with each boss stage cleared at its bound and $040C set to 3 where the stage's last door would set it, the game's room change loads the boss room; Felix placed there at x 290 with the boss up sets the clear flag the next frame, the fight's step $0411 still at 0, and the next stage loads.Verified“Felix the Cat (USA)” · 1625M, replayed in FCEUXrevised
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $F7FF-$F840: the test reads Felix's x, $32, and the bound; nothing about a boss; fixed bank $F841-$F856: with $040C at 3, jump to $FA07; with $040C or $040D odd, to $F9F7; otherwise the hop at $F857; fixed bank $FA07-$FA1F: unless $040D is 8, set $0411 to $FF; add 1 to $0411, set $040D to 8, and load the room. We don't reproduce the bytes.
each boss fight
Measured by a script in MesenCE 2.2.1 (build 4b8a196), on Felix the Cat (USA) (SHA-1 b57b1c6e6933…). It fails if the result disagrees with the claim.
The numbers come from the run; its author, an AI model, checked the script measures what the claim says, 2026-10-25.
Revised after a check by a second AI model, 2026-10-25.
Revised after a check by a second AI model, 2026-10-25.
In the claim ledger
^ a bIn each of the seven boss rooms, the map's columns 14 to 31, x 224 to 511 of its 512 px, are solid from top to bottom, and so is column 0. The wall test (felix-the-cat/wall-test) stops Felix at x 215, where the point 8 px ahead of him reaches the wall. In Mesen, moving right at his top speed of 533/256 px a frame from x 215, he stays at 215 at every height, from above the map to below it.Verified“Felix the Cat (USA)” · 1625M, replayed in FCEUXrevised
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $F251-$F290: the map lookup the wall test uses (felix-the-cat/collision-map); fixed bank $D0EB-$D15F: moving right, test the tile at x + 8; if it blocks, subtract the x speed from x. We don't reproduce the bytes.
each boss fight
Measured by a script in MesenCE 2.2.1 (build 4b8a196), on Felix the Cat (USA) (SHA-1 b57b1c6e6933…). It fails if the result disagrees with the claim.
The numbers come from the run; its author, an AI model, checked the script measures what the claim says, 2026-10-25.
Revised after a check by a second AI model, 2026-10-25.
In the claim ledger
^Each frame of play, after the mover adds Felix's x speed and push to his x, the fixed bank's $D05F checks him against the screen's edges or the map. With his x's high byte past the bound's, or equal to it with a low byte of $DB or more outside a boss fight (and a few other cases), the game walks him right (the auto-walk) and tests the map. Short of that, an x less than 8 or at least 240 past $B7:$B9 sets his x speed to 1 px a frame back inward, and the map isn't read that frame. Otherwise, moving right, it reads the map 8 px ahead of him, normally at y + 1, y − 8, and y + 13 (moving left, 8 px behind), and if a tile there blocks, it subtracts that frame's x speed from his x again. Then $D191 moves x 1 px toward 7 or 8 px into its 16 px column.Code“Felix the Cat (USA)”revised
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $D023-$D02B, in Felix's update: JSR $D87E, JSR $D90F (the mover), JSR $D05F; fixed bank $D049-$D0EA: past the bound's page, or in it at x low byte $DB or more unless $040D is 1, $040D + $0411 is 8 (a boss fight), or the stage index is $17, hold Right and accelerate (the auto-walk), then the map test; otherwise x - $B7:$B9 below 8 sets the x speed to $0100, at $F0 or more to $FF00, and returns; fixed bank $D0EB-$D15F: with the x speed at 0, test both sides; positive, the tile at x + 8 (mask $FD); negative, x - 8 (mask $FB); on a hit, subtract the x speed from the fraction and x, then $D191; fixed bank $D191-$D1BD: fraction to $80; x's low nibble 7 or 8 stays, below 7 gains 1, above 8 loses 1; fixed bank $D1BE-$D213: the tile at y + 1; then y - 8 unless $03C3 is 7; then y + 13 unless $03B0 is set; nonzero when one blocks. We don't reproduce the bytes.
Checked against the evidence by its author, an AI model, 2026-10-25.
Revised after a check by a second AI model, 2026-10-25.
In the claim ledger
^The map that Felix's tile tests read is 32 columns of 16 px by 24 rows of 16 px in cartridge RAM at $6000-$63FF, a ring that repeats every 512 px of x. A tile's type is the low nibble of its entry in a table at ($CA). Types 1, 14, and 15 block both ways; type 4 blocks only moving left, and type 5 only moving right. A point above the map reads the top row, and one 384 px down or more reads the bottom row, where any nonzero type counts as 1.Code“Felix the Cat (USA)”
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $F251-$F290: row from y ($07:$06): negative, row 0; below 256, y / 16; 256-383, 16 + (y - 256) / 16; else row 23 with a nonzero type as 1; address $6000 + (x high bit 0) * $200 + (x low / 16) * $20 + row; type = ($CA),tile AND $0F; fixed bank $CF81-$CF90, the blocking bits by type: 00 01 00 00 02 04 00 00 00 00 00 00 00 00 01 01; moving right tests them with $FD, left with $FB. We don't reproduce the bytes.
Checked against the evidence by its author, an AI model, 2026-10-25.
Checked by a second AI model, 2026-10-25.
In the claim ledger
^Felix's push $041D comes from one routine, in PRG bank 12: a platform whose x swings with the frame counter sets it, while Felix rides, to the change in its x that frame, and the object pass clears it again afterward. The mover adds it to Felix's x, and the wall test never takes it back (felix-the-cat/wall-test). In FCEUX's replay of the 1625M movie the push was 1 px either way, and it came only in the main areas of stage indices 1, 2, 7, 9, 10, 12, 18, and 22, never in a boss room.Code“Felix the Cat (USA)” · 1625M, replayed in FCEUX
How we know
In the cartridge (“Felix the Cat (USA)”): bank 12 $9165-$91B2: save the x low byte in $01; x = the base $06F2:$06DC + ($37 / 2, mirrored by $37 bit 6) AND $1F; with $0708 bit 4 set and x moved, $041D = x - $01; fixed bank $E12B-$E155: update slots 6 to 21, then 0 to 5, then zero $0420-$0423 and $041D; fixed bank $D90F-$D93D: the mover adds $06C6 + $041D to Felix's x. We don't reproduce the bytes.
every nonzero write to $041D
Checked against the evidence by its author, an AI model, 2026-10-25.
Checked by a second AI model, 2026-10-25.
In the claim ledger
^A door in a boss room leads back into the same room. Pressing Down on a door tile sends Felix down it, and the door's kind picks the room change. In a boss room ($040D = 8), $CABF gives every door kind 2 except in stage index 22, and kind 2 is a hop back up where he went down. Only kind 3 moves the boss step on (felix-the-cat/boss-step), and $CB90 gives it only to a door in a main area, with the step at 0. Stage index 5's boss room has a door tile where Felix comes in. In FCEUX, Down on it during the fight sends him down and back up at x 48, with the fight still on.Code“Felix the Cat (USA)” · 1625M, replayed in FCEUXrevised
How we know
In the cartridge (“Felix the Cat (USA)”): fixed bank $CABF-$CAC8: with $040D at 8, go to $CB9F; fixed bank $CB9F-$CBA4: unless the stage index is $16, go to $CB82; fixed bank $CB82-$CB86: kind 2 into $066E, then $CB0C, which puts Felix in state $0D (going down); fixed bank $F841-$F856: kind 3 goes to $FA07; kind 2 with $040D at 8 is even, so the hop at $F857. We don't reproduce the bytes.
frame 15184, the movie stopped there
Checked against the evidence by its author, an AI model, 2026-10-25.
Revised after a check by a second AI model, 2026-10-25.
In the claim ledger
^$0411 is a boss stage's step: 0 in the fight, 1 once the boss is beaten, and 2 in the room after. Only two instructions add to it: $A20D in PRG bank 13, in the routine that runs when the boss is beaten, and $FA13, in the room change that $040C = 3 asks for. A door asks for it only in a main area (felix-the-cat/boss-room-door); in the boss room, bank 13's $A1B9 stores the 3. Every store to $0411 writes 0, or $FF that $FA13 lifts to 0 at once. In FCEUX's replay of the 1625M movie, in World 1, the step went from 0 to 1 at $A20D on frame 7,643; on frame 7,880 $A1B9 set $040C to 3, and $FA13 took the step to 2.Code“Felix the Cat (USA)” · 1625M, replayed in FCEUXrevised
How we know
In the cartridge (“Felix the Cat (USA)”): bank 13 $A201-$A20F (mapped at $A000): with $0776,X bit 3 set, play sound $10 and INC $0411; bank 13 $A1B2-$A1BC: $0616,X = 0, $040C = 3; fixed bank $FA07-$FA1F: unless $040D is 8, $0411 = $FF; INC $0411; $040D = 8. We don't reproduce the bytes.
frames 7500-7960, writes to $0411 and $040C
Checked against the evidence by its author, an AI model, 2026-10-25.
Revised after a check by a second AI model, 2026-10-25.
In the claim ledger
^In Randil's 1625M movie, replayed in FCEUX, the seven boss fights last 627 to 733 frames from the first frame of play in the boss room to the frame the boss is beaten ($0411 reaches 1), 4,982 frames in all.Our research1625M, replayed in FCEUX
How we know
each boss fight
Measured by a script. It fails if the result disagrees with the claim.
Checked against the evidence by its author, an AI model, 2026-10-25.
Checked by a second AI model, 2026-10-25.
In the claim ledger
^ a b c d e f g h i j k l m n o p q r s t u v w x y z 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70Replayed in FCEUX, Randil's 1625M movie passes 23 stages in 9 worlds of 3, 3, 3, 3, 3, 2, 2, 1, and 3 stages. For each stage the table gives the frame play starts (game mode $28 reaches 5) and the frame the clear flag goes up; the last stage runs to the movie's end at frame 81,074.Our research1625M, replayed in FCEUX · TASVideos publication 1625
How we know
the whole movie
NES Felix the Cat by Randil in 22:29.01
publication page · archived copy ↗
Measured by a script. It fails if the result disagrees with the claim.
Checked against the evidence by its author, an AI model, 2026-10-25.
Checked by a second AI model, 2026-10-25.
In the claim ledger

Sources

Code

1992. “Felix the Cat (USA).” · licence, all uses

Primary

Advance, Frame. 2026. “Felix the Cat (USA): TASVideos 1625M replayed in FCEUX 2.6.6.” · licence, all uses

Secondary

Randil. 2010. “#1625: Randil's NES Felix the Cat in 22:29.01.” TASVideos. original · archived · licence, all uses
KAGE-008. 2019. “#6487: KAGE-008's NES Felix the Cat (Dragon Co.) "glitch exit" in 04:33.80.” TASVideos. original · archived · licence, all uses