rhetenor/creaturedex
1
0
Fork 0
Code Issues 22 Pull Requests Packages Projects 1 Releases Wiki Activity
Page: NFC Payload Layout
Pages
Displays NFC Payload Layout Prior art ToDo software arch
Clone
3
NFC Payload Layout
ede1998 edited this page 2026-07-20 17:37:13 +02:00
Table of Contents

Creature Cards NFC Payload Layout

This document summarizes the parts of the mysteryhack.com:cc1 NFC payload that are currently understood from the sample cards.

Visual Map

flowchart LR
  A[Bytes 0-1<br/>E9 24<br/>Event encoding<br/>GPN24] --> B[Byte 2<br/>Palette / type selector]
  B --> C[Bytes 3-4<br/>Card UUID suffix<br/>47 F2 / DA 45]
  C --> D[Bytes 5-8<br/>Reserved / padding]
  D --> E[Bytes 9-730<br/>Sprite blob<br/>722 bytes<br/>Packed 38x38 4bpp<br/>Hex range: 0x09-0x2DA]
  E --> F[Bytes 731-784<br/>Packed card text<br/>72 chars in 6-bit alphabet<br/>Name + 3 traits<br/>Hex range: 0x2DB-0x310]
  F --> G[Bytes 785-808<br/>Secret field<br/>UTF-8, up to 24 bytes<br/>Hex range: 0x311-0x328]
  G --> H[Bytes 809-857<br/>Opaque trailer<br/>Remaining metadata still not fully identified<br/>Hex range: 0x329-0x359]

Byte Ranges

Offset Length Meaning Notes
0x00-0x01 2 Event encoding E9 24 maps to the event identifier GPN24.
0x02 1 Palette / card type byte In the current samples, 0x01 maps to Default and 0x03 maps to CYBER. The full palette order appears to be one-based: Default, Blueprint, CYBER, Nature, Fossil, Ghost, Daemon, Fairy.
0x03-0x04 2 Card UUID suffix Sample values are 47 F2 for Blue Portal and DA 45 for GLaDOS.
0x05-0x08 4 Reserved / padding Not yet decoded.
0x09-0x2DA 722 Sprite blob Packed 38x38 image data. This is embedded directly in the payload and matches the sprite PNG metadata.
0x2DB-0x310 54 Packed card text LSB-first 6-bit packing using the alphabet ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-. This decodes to 72 characters total: 24 for name, 16 for trait1, 16 for trait2, 16 for trait3.
0x311-0x328 24 Secret UTF-8 text, right-padded with 0x00 when shorter than 24 bytes.
0x329-0x359 49 Opaque trailer Remaining metadata that is still not fully identified.

Known Samples

Card Event bytes Palette byte UUID suffix Quote text
Blue Portal E9 24 01 47 F2 Speedy thing goes in
GLaDOS E9 24 03 DA 45 The cake is a lie

Details on image data

  • 38x38px
  • 8 color palettes x 16 colors
  • Color palette is defined by the creature's type.
  • Pixel encoding?

"Official" documentation