Tool-assisted game movies
When human skills are just not enough

Submission #6497: Aglar, MESHUGGAH & Riyan's NES Disney's DuckTales in 06:43.49

Console: Nintendo Entertainment System
Game name: Disney's DuckTales
Game version: USA
ROM filename: DuckTales (U).nes
Emulator: FCEUX 2.2.3
Movie length: 06:43.49
FrameCount: 24249
Re-record count: 9947
Author's real name: Mikael Johansson, Oliver H. & Riyan
Author's nickname: Aglar, MESHUGGAH & Riyan
Submitter: Riyan
Submitted at: 2019-08-29 20:26:27
Text last edited at: 2019-09-14 11:48:10
Text last edited by: feos
Download: Download (6023 bytes)
Status: decision: rejected
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Author's comments and explanations:

Improved TAS

(Link to video)
DuckTales is a classic game in which Scrooge has to collect treasures from all over the world. Some of the levels are not completely straightforward, and collecting items is sometimes necessary before proceeding. His cane also doubles as an almighty pogo stick that can be used in various ways, which makes jumping a lot more fun.

This is the seventh TAS of DuckTales.

This is a 13 seconds improvement over the previous movie due to a glitch that can be performed by pressing the up button on the second controller that will allow Scrooge to wrap when climbing ropes and vines.

  • Aims for fastest time
  • Takes damage to save time
  • Manipulates luck
  • Abuses programming errors
  • Plays at hardest difficulty

feos: Judging...

feos: Replacing the movie with an improved version.

feos: It looks rather cool indeed, but I can't consider this a glitch.

This technique is known at least since 29.03.14. It was later added to tcrf.net. ROM-hacker CaH4e3, who was probably the original finder of the trick, called it a debug leftover.

Firstly, I trust his expertise.

Secondly, we looked for more input combinations like this, and there is a couple. Both official release and prototype check the second controller for pressing Up while falling to skip screen scrolling in certain situations, and Left+Right/Up+Down to filter those inputs out. The prototype also checks for A+B to enable invincibility. The checks are direct and explicit:

  07:E704: LDA PlayerMovement
  07:E707: AND #$04           ; check falling flag
  07:E709: BEQ $E718          ; if zero, exit subroutine
  07:E70B: LDA $17            ; read controller 2 state
  07:E70D: AND #$08           ; check Up button
  07:E70F: BNE $E718          ; if non-zero, exit subroutine
  07:E711: LDA PosY           ; load vertical player position
  07:E714: CMP #$E0           ; subtract from 0xE0
  07:E716: BCS $E719          ; if result is below zero, handle screen scrolling
  07:E718: RTS                ; exit subroutine
  07:E719: LDY $F1            ; handle screen scrolling
If you're falling while holding Up on the second controller, and your vertical position is below a certain value, the screen won't scroll down like it does normally, you'll just keep falling until your vertical position wraps around. There seem to be extra conditions like the screen will only scroll if there's a bottom room, but this doesn't change the fact that this check is intended. So it's not a bug, but a feature.

Since this feature is not mentioned in the manual, and DuckTales is a single-player game, second controller input isn't intended for normal play.

It doesn't give the player any real advantage, so we can't call it a cheat code, but we can call it a debug code leftover judging by various factors mentioned in this post. Since we don't allow using debug codes, this movie has to be rejected.

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