Pokemon Yellow is a pocket universe with its own rules. In it, you can buy and sell items, train Pokémon, defeat other trainers - but you cannot change the rules of the game itself. You can't build yourself a house, change your music, or even change your clothes. More precisely, it was intended that way. In fact, there is a sequence of valid commands (such as moving from one place to another and manipulating objects) that allows you to turn the game into Pacman, Tetris, Pong, MIDI player and whatever.
There is a speedrun Felipe Lopes de Freitas (p4wn3r) , in which Pokemon Yellow is completed in 1 minute 36 seconds. This speedrun is based on the following hack: Normally, the player's inventory is limited to 20 items. But there is a bug that allows you to ignore this limitation and treat the memory located immediately after the inventory as if it were a list of items. Accordingly, standard object manipulation allows this memory to be rewritten. Speedrunner uses this opportunity to force the door from the starting room to transfer him to the final location, in which he can only listen to congratulations.
When I first saw this speedrun and realized that Gameboy memory can be manipulated with just a list of items, without any external tools, I decided to see if I could improve the p4wn3r techniques. Here's what happened:
Gameboy — . , — , . , [62 16 37 224 47 240 37 230 15 55]
, , , A. , - , . - ( ) Gameboy — , (, ) Pokemon Yellow.
-, ? , (, , ..) :
item-one-id (0-255)
item-one-quantity (0-255)
item-two-id (0-255)
item-two-quantity (0-255)
.
.
.
, :
lemonade x16
guard spec. x224
leaf stone x240
guard spec. x230
parlyz heal x55
— . , , ID . - , , 2-3 . , , 92 ; , .
— , . , , , , . , , .
!
, Lp/k. , . , , p4wn3r: , . 8 10 , 20- ( ). Celadon Dept. store. p4wn3r “ ” , .
, 0x00, . , 0xFF 0x00 . , , . 255 0x00- . 2 0x00 414925 , :
+-------------------+----------+
|##| Item | Quantity |
+--+----------------+----------+
|1 | TM02 | 98 |
|2 | TM37 | 71 |
|3 | TM05 | 1 |
|4 | TM09 | 1 |
|5 | burn-heal | 12 |
|6 | ice-heal | 55 |
|7 | parlyz-heal | 99 |
|8 | parlyz-heal | 55 |
|9 | TM18 | 1 |
|10| fire-stone | 23 |
|11| water-stone | 29 |
|12| x-accuracy | 58 |
|13| guard-spec | 99 |
|14| guard-spec | 24 |
|15| lemonade | 16 |
|16| TM13 | 1 |
+--+----------------+----------+
, . — . , , A, B, start select. 4 ; 200 , , . , 8 , . , , , , .
, Celadon mansion ( , ). . , , . , , .
, Gameboy (, ) . — , . http://hg.bortreb.com/vba-clojure
, , vba-rerecording. C, Java JNI. : Gameboy, . , Java .
JNI clojure, vba-rerecording. , C . , , , . , . , , Viridian City :
(defn-memo viridian-store->oaks-lab
([] (viridian-store->oaks-lab
(get-oaks-parcel)))
([script]
(->> script
(walk [↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓
← ← ← ← ← ← ← ← ←
↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓
← ←
↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓
↓ ↓ ↓ ↓ ↓ ↓ ↓
→ → → → → → → →
↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓
← ← ← ← ←
↓ ↓ ↓ ↓
])
(walk-thru-grass
[↓ ↓ ↓ ↓ ↓ ↓ ↓])
(walk [↓ ↓ ← ↓ ↓ ↓ ←
↓ ↓ ↓ ↓ ↓ ↓
→ → → ↑])
(do-nothing 1))))
, :
(defn-memo hacking-10
([] (hacking-10 (hacking-9)))
([script]
(->> script
begin-deposit
(deposit-held-item 17 230)
(deposit-held-item-named :parlyz-heal 55)
(deposit-held-item 14 178)
(deposit-held-item-named :water-stone 29)
(deposit-held-item 14 32)
(deposit-held-item-named :TM18 1)
(deposit-held-item 13 1)
(deposit-held-item 13 191)
(deposit-held-item-named :TM02 98)
(deposit-held-item-named :TM09 1)
close-menu)))
, , . , , 99. , :
(defn pc-item-writer-program
[]
(let [;;limit 75
limit 201 ;; (item-hack 201 is the smallest I could make this.)
[target-high target-low] (disect-bytes-2 pokemon-list-start)]
(flatten
[[0x00 ;; (item-hack) no-op (can't buy repel (1E) at celadon)
0x1E ;; load limit into E
limit
0x3F ;; (item-hack) set carry flag no-op
;; load 2 into C.
0x0E ;; C == 1 means input-first nybble
0x04 ;; C == 0 means input-second nybble
0x21 ;; load target into HL
target-low
target-high
0x37 ;; (item-hack) set carry flag no-op
0x00 ;; (item-hack) no-op
0x37 ;; (item-hack) set carry flag no-op
0x00 ;; (item-hack) no-op
0xF3 ;; disable interrupts
;; Input Section
0x3E ;; load 0x20 into A, to measure buttons
0x10
0x00 ;; (item-hack) no-op
0xE0 ;; load A into [FF00]
0x00
0xF0 ;; load 0xFF00 into A to get
0x00 ;; button presses
0xE6
0x0F ;; select bottom four bits of A
0x37 ;; (item-hack) set carry flag no-op
0x00 ;; (item-hack) no-op
0xB8 ;; see if input is different (CP A B)
0x00 ;; (item-hack) (INC SP)
0x28 ;; repeat above steps if input is not different
;; (jump relative backwards if B != A)
0xED ;; (literal -19) (item-hack) -19 == egg bomb (TM37)
0x47 ;; load A into B
0x0D ;; dec C
0x37 ;; (item-hack) set-carry flag
;; branch based
on C:
0x20 ;; JR NZ
23 ;; skip "input second nybble" and "jump to target" below
;; input second nybble
0x0C ;; inc C
0x0C ;; inc C
0x00 ;; (item-hack) no-op
0xE6 ;; select bottom bits
0x0F
0x37 ;; (item-hack) set-carry flag no-op
0x00 ;; (item-hack) no-op
0xB2 ;; (OR A D) -> A
0x22 ;; (do (A -> (HL)) (INC HL))
0x1D ;; (DEC E)
0x00 ;; (item-hack)
0x20 ;; jump back to input section if not done
0xDA ;; literal -36 == TM 18 (counter)
0x01 ;; (item-hack) set BC to literal (no-op)
;; jump to target
0x00 ;; (item-hack) these two bytes can be anything.
0x01
0x00 ;; (item-hack) no-op
0xBF ;; (CP A A) ensures Z
0xCA ;; (item-hack) jump if Z
target-low
target-high
0x01 ;; (item-hack) will never be reached.
;; input first nybble
0x00
0xCB
0x37 ;; swap nybbles on A
0x57 ;; A -> D
0x37 ;; (item-hack) set carry flag no-op
0x18 ;; relative jump backwards
0xCD ;; literal -51 == TM05; go back to input section
0x01 ;; (item-hack) will never reach this instruction
]
(repeat 8 [0x00 0x01]);; these can be anything
[;; jump to actual program
0x00
0x37 ;; (item-hack) set carry flag no-op
0x2E ;; 0x3A -> L
0x3A
0x00 ;; (item-hack) no-op
0x26 ;; 0xD5 -> L
0xD5
0x01 ;; (item-hack) set-carry BC
0x00 ;; (item-hack) these can be anything
0x01
0x00
0xE9 ;; jump to (HL)
- 0x00 0xFF. 0x00 , , . 0x00 — NO-OP, , . 0xFF . : , , , , :
pokeball x2
- 0xFF, , :
pokeball x1
pokeball x1
pokeball x1
0xFF .
, Gameboy, — . MIDI, GameBoy, http://www.everyponysings.com/. MIDI-, . — PNG- Gameboy- , . , , ( http://hg.bortreb.com/vba-clojure).