Fist II: The Legend Continues: the source

Current truth for this game. The workflow lives in kit/skills/; how this understanding developed lives in agent-history.md. Every fact names the routine or table it comes from. Unless marked live, a fact comes from reading the code in work/f2-entry.vsf, the Adventure hand-over.

Build

The Mindscape disk (orientation.md). The Adventure load fills memory from $0400 to $FFF8, the RAM under the I/O chips and the KERNAL included. The game never switches the I/O out: $01 is written only by the loader and the start-up ($C459, $C469), and stays $15 in play (live). So only the video chip reads the RAM at $D000-$DFFF.

Memory layout

Timing and structure

• The game runs two tasks, each on its own stack: the main loop (play_loop $21E2) and a background task at $12CA-$1540 that shifts the hidden screen one column at a time between coarse scroll steps. $14E8/$1503 switch between them; the status-band interrupt reaches $1503 when $12CA has overwritten its RTI at $3D86 with a NOP ($12E0 puts it back).
• The screen is double-buffered: $74 holds $CC or $F0 (live: both seen), and $D018 is built from $C0 OR $1536 at $3BFD.
• Raster interrupts chain by rewriting $FFFE/$FFFF. $3BD4 starts the play area and $3D21 the status band; about thirteen more handlers are templates that move sprites 1-3 and 5-7 down the screen, their operands rewritten each frame by $4049-$4877 (live: five handlers in one frame capture, which the page redraws pixel for pixel).
• RESTORE pauses: the NMI $3C23 toggles $0416 and play_loop waits at $2201 (live).

Controls

• Joystick port 2 ($3396); the move map at $33C3 turns a joystick position, with and without fire, into a move, and $33E3 says which moves are allowed from which.
• F5 restarts the game ($2444, keyboard row 0 reading $BF).
• RESTORE pauses (live).
• read_joystick also reads port 1 for fighter 1 when $0455 is 0; no path to that was found.

Fighters

• A fighter is nine hardware sprites. 44 move scripts ($AF46) are lists of 4-byte steps (time, pose, dx, dy); 73 poses ($B210) name a sprite frame for each of the nine slots.
• The 229 frames at $8000-$AF0F are zero-run packed: a non-zero byte is copied, $00 n writes n zeros, 63 bytes out. Frame i starts at $8000 + $B661[i] × 256 + $B57C[i] (checked: frames 1, 2, 143 and 228).
• Frames are stored facing one way. The other way is drawn by reversing each row's three bytes and passing each through $BF00, which reverses the four pixel pairs of a byte (checked, all 256 entries).
• The fighters are drawn with up to seven screen-split layouts, chosen by the vertical gap between them ($40F6).
• Hits: $379C reads the strike reach for the move and animation frame from $7CA6 (facing each other) or $7E53 (same way); $80 means no strike; otherwise the reach is compared with the fighters' separation. Collisions between sprites come from $D01E ($3328, $3F99).
• A hit landed by the hero scores 100 × the move's value in $051D.

Energy, lives and scrolls

• The hero starts with 47 energy and maximum 47 (live); it comes back one point every 128 frames ($2D14). Meditating sets the maximum to 47 + 4 × the opponents beaten (rounded down to even), at most 127 ($396F).
• An opponent starts with 31-63 energy, 64 more after 16 defeats ($274E; live: 63).
• Lives start at 1 (live), gain one for each scroll delivered to its chamber ($2CCD) and lose one per death ($353E). The hero restarts in the last meditation chamber visited ($2D33).
• Meditation chambers are rooms $44-$4B, one per scroll. Scroll flags $0405-$040C: 1 found, $80 delivered.
• In area 5 the screen flashes and the hero loses energy every 10 frames until he dies, unless scroll 8 has been delivered ($2CE4).
• Hazards cost 2 or 10 energy; an attack at its striking frame knocks one away ($2A57, $2BB4, $2A87).
• Encounters: 54 three-byte records at $E609 (flags, room, position): opponents, hazards and scrolls lying in rooms.

The world

• 123 screens, each in one of 48 areas ($4A71). Areas 0-7 use scenery set 0, 8-29 set 1, 30-47 set 2 ($196F, thresholds $0E44 = 8, $0E45 = 30; live: screen 94 area 28 at the start, screen 100 area 30 at the first opponent). Each set has shapes of screen codes, composite objects, and per-area lists of objects (X, Y, type).
• Per-screen exit lists at $4AEC: type, trigger column, destination screen and column.
• A zone sets the tune, the border colour, sprite priority and scenery.
• Drawing a room (setup_room_data $0FEC, draw_room $1556): $0F68[area] objects, their X, Y and type from three lists whose offsets are words indexed by twice the area within its set (set 0 base $5BD7, lists $5BA7/$5BB7/$5BC7; set 1 $68D8, $6854/$6880/$68AC; set 2 $78E2, $7876/$789A/$78BE). A type below $80 is a shape: a block of screen codes, width by height, found through the set's tables at $0F32 (load_zone_tables $124A). A type $80 and up is a group of shapes, each with its own column and row offset; $FF is an empty slot. Rows stop at 20. The character set is $D800, $D000 or $E000 by set ($0E40 into $D018, $3BFD). Colours: a list of rows per room or area, each byte giving rows (high five bits) and colour (low three, plus 8 for multicolour), with the three shared colours from the set's tables or, in set 0, from a scheme chosen by area or by the room's nibble at $0E52. Scheme 8 is dark, and becomes scheme 2 once scroll 7 is delivered ($10D7-$10EA). The chambers (area 6) get extra colour cells painted ($1703). Checked: drawn this way from listing.json, the start of room 94 and the stone wall of room 100 match the screenshots in reference/.
• How far the screen scrolls: a wall stops the view at its column less $0ABD[type] on the left and plus $0ABD[type] on the right, less 40 for the scroll position (find_room_barriers $087A).

Play, from the manual and the code

• The C64 manual (Lemon64's docs image, read 1 October 2026, given by the contributor) names the moves: fire up, up-back forward somersault, up jump/climb up, up-forward high punch, back walk back, forward walk forward, down-back reverse somersault, down duck/climb down, down-forward jab; fire down, up-back back kick, up flying kick, up-forward high kick, back roundhouse/turn, forward mid kick, down-back rear sweep, down sweep, down-forward low kick.
• Scroll icons ($054B/$0553, status font $E800) are trigrams, top line first: scrolls 1-8 are Ch'ien, Sun, Kan, Chen, K'un, Ken, Li, Tui. The manual lists them as Ch'ien, Sun, Chen, Kan, Ken, K'un, Li, Tui.
• Defeat counter $048C: cleared at game start ($2135), +1 at each defeat ($3527), held at 31 ($352D-$3533). Read by meditation ($396F), opponent energy (+64 from 16, $2755) and the respawn test. The manual says meditation counts defeats "since your last meditation"; the code counts them all.
• Respawn: scan_encounters ($27F5) skips a done record (flags bit 7) unless it is not a scroll (bit 6 clear), $048C >= 30 and random AND $81 is 0, one time in four ($2820-$282C). A record is marked done only at a defeat ($3522).
• Hordes: a record with low nibble $0A sets $0472 = 10 ($2875); each defeat brings the next until it runs out, or at once once scroll 5 is delivered ($27AD, its only reader). No record in the table has low nibble $0A, and the only writes to it set or clear bit 7 ($278B, $2C3C, $3524), so no horde occurs in this copy and scroll 5's power has nothing to act on.
• Room 76 (area 7): its two type-17 drops (columns 10 and 19) lead to room 60 and are the only way into the volcano. Falling into one tests scroll 3 ($0659); undelivered, energy $0412 is set to 0 ($0660). Bill McIntosh (Stuckey's thesis, 2016) remembered this as a trapdoor that "killed the player instantly", followed by nine unbeatable warriors; the warriors are not in this copy.

Sound

• Music: a three-voice driver at $F400, called once a frame from $3D21. Three tunes, chosen by $FF (live: 3 in the jungle); tempo from $F42F; sequences of patterns; 17 instruments of 21 bytes with pulse-width sweeps, glide, vibrato and a filter sweep. The note table at $F4C9 is one equal-tempered octave (live check of the ratios), doubled per octave; note lengths at $F4D5.
• Tunes by zone ($1247): zone 0 (areas 0-7) tune 1, zone 1 (8-29) tune 3, zone 2 (30-47) tune 2; area 6, the temples, tune 2 ($11FC-$1202). Tempo 2, 2, 5 frames a tick. Tune 1 uses instruments 0-7, tune 2 9-11, tune 3 12-16; instrument 0 sweeps the filter from voice 3's envelope ($D41C, source 3).
• The port in reference/fist-music.js matches the driver run in kit/c64/cpu6502.js, all 25 SID registers after each of 30,000 frames of each tune (tests/music.js).
• Sampled sounds: a CIA 1 timer B interrupt ($3D8B) flips the SID volume between two levels, each sample byte choosing the time to the next flip through the period table at $0200/$0300. play_sample $3DB8 starts one, with a rise, hold and fall.

Hardware register census

Towards a solution

Read from the game's tables, with the live tests named.

Where the scrolls lie (encounter records with flags $60-$67 at $E609; flags AND 7 is the scroll number, byte 2 the map position):

What each delivered scroll opens (the code that tests $0405+n):

The map. Each of the 123 rooms has an exit list at $4AEC: type, column, destination room, arrival column (read with find_room_exits $1A06; tested against the hero's column $E5 by scan_room_exits $0576). Walls are the 2-byte records of the room's item list ($501E); the hero stops at a wall's column plus $0AC7[type] from the left and minus $0ABD[type] from the right ($087A-$08DF; live: stopped at column 75 by the wall at 77 in room 101). Barriers are the 3-byte records with bit 7 set: type 1 breaks to any attack at its striking frame while the hero is against it ($0A2E; live: room 104), types 3 and 7 only once scroll 1 or 4 has been delivered.

Exit types, by what scan_room_exits does with them:

A drop takes the hero only while he is walking with his feet on the floor: $92 is his height on the screen, $4E (78) when standing, and $371D tests it. A forward somersault (stick up and back) lifts him off the floor for about ten columns, and so carries him over a hole or a 7-column drop (live: from column 48 over the hole at 52 in room 103; from column 112 over the drop at 115-121 in room 85, landing at 122). No tested move crosses an 11-column drop.

Picking up a scroll. The encounter scan ($27F5) shows a room's scroll when the screen's map position $72 plus 0 (walking left) or 41 (walking right, $2961) equals the scroll's map position; the hero picks it up by touching it (sprite collision, $2C25), which sets its flag to 1. Delivering it to its chamber sets $80 and adds a life.

Tested in the emulator. A breadth-first search over the exit lists, walls, barriers, drops and the gates above, with a script that drives the joystick along its route. For route testing the script marks every encounter except the scrolls as done and holds the hero's energy, so fights were not played. On 1 October 2026 it collected and delivered five scrolls in this order, ending with scrolls 1, 2, 4, 6 and 8 flagged $80 and 6 lives:

Two traps decide the route. Arriving in room 84 from room 4 carries the hero on to room 87, so scroll 4 (at 124, beside the drop at 112-122) is reached only from room 112. In room 85 the drop at 115-121 takes the hero to room 111 unless he somersaults it.

The crevice in room 79. Scrolls 5 and 7, chambers 72 and 74, the volcano rooms 60-63 and the ending, room 122 ($2DB5), lie in a region (rooms 8, 16, 18, 30-36, 60-63, 72, 74, 76, 88, 95-99, 107, 117-120, 122) whose only way in, by the exit tables, is room 79's right-hand exit at 171 to room 117. Room 43's exit at 88 (type 5, stick up and right) arrives in room 79 at column 0, left of room 79's drop at 18. That drop is 11 columns wide, but with scroll 6 delivered scan_room_exits narrows it to columns 18-24 ($067B), which the forward somersault crosses; the drop blinks the scroll-6 icon as a hint ($0491/$0492, blink_icons $2D57). Past it, the type-7 barrier at 109 breaks once scroll 4 is delivered. With that crossing modelled, the search (solver/solve.py, reading the committed listing) finds all eight scrolls in the order 1, 8, 2, 4, 3, 6, 7, 5 and reaches room 122 through rooms 34, 97-99, 76 and 60-63. The crossing, scrolls 3, 7 and 5 and the ending have not been driven in the emulator. Two outside sources agree: the key of a hand-drawn map by Master Lee and hiTCH-HiKER (December 2008, given by the contributor) names scroll 6 "crossing the rock crevice", and Magnus Andersson's GameFAQs walkthrough (2007) has "a middle plattform at the waterfall. Jump across and continue right."

The slide in room 77 is not the way in: its exit at 222 carries the hero into the drop at 233, which lands him in room 79 at column 21, inside the crevice, and he falls on through to room 82 (live, walking, standing, ducking, every stick direction). Room 77 refuses jumps and attacks (live).

The same map's key matches the other scrolls to the code: 1 destroying stone heaps (type-3 barriers), 2 the way across to the river (room 52), 3 keeping energy for the last opponent (area 7), 4 kicking trees down (type-7 barriers), 5 more fighting strength (chains end early), 7 lighting the dark rooms (a zone's colours), 8 surviving the poison rooms (area 5).

Open questions

• Two AI combinations: $31F2 stores into $B4 without ,X, so combination 8 sets up combination 5 in the hero's slot.
• $4A39 makes a negative step positive in place.
• Only voice 1 restarts its vibrato on a new note ($F6F0).
• 29 uncompressed head sprites at $B746-$BEBF, a character set at $E000-$E607 and 1,200 bytes at $E910 have no reader found.
• An older build's start-up at $C280-$C3BA is never reached.
• How the port-1 second fighter would be switched on.

Live tests

The cast

• All fighters share the 229 body images and the 73 poses ($B210, nine tables of 73). A fighter's graphics set $4E,X (set_fighter_graphics $269D) picks the body colour $5E ($26C3: 2, 9, 11, 2, 9), the head sprite's colour $48 ($26B4: 1, 2, 11, 5, 1) and the head images' address ($26B9/$26BE: $B746, $BD46, $B8C6, $BA46, $BBC6, six unpacked 64-byte images each). The hero is set 0 ($26D0); an opponent's set is bits 4-5 of its record plus 1 ($2716-$2723): sets 1-4 have 12, 12, 8 and 8 of the 40 opponent records.
• Per pose, $B533 gives the head image (low nibble - 1, none when 0), mirror (bit 4, XOR facing) and upside down (bit 5); $B4A1 and $B4EA the head's signed X and Y offset from the body's top left (copied $02-$21 to $22-$41 at $3FA8; placed at $45DF, mirrored as 48 - X at $4648). Body rows are 21 lines apart, columns 24 pixels. Checked: drawn this way, the five sets in pose 0 match the hero in the reference screenshots; live (2 October 2026, booted from work/fist-mindscape.g64): the opponent in room 94 (record flags $10, set 2) is drawn grey with the grey hood, as the page draws set 2. Sets 1, 3 and 4 have not been compared.

Cheats

Pokes that change the game within its own parameters. Each one names the variable it changes and whether it has been tested live. Untested pokes are labelled as candidates.