This is how tutorials show changes made to files:

 this is some code
-delete red - lines
+add green + lines

Contents

• Assembly programming
• How to add a new…
• Port from Pokémon TCG 2
• Gameplay changes
• Improvements
• Miscellaneous
• To do

Assembly programming

• Opcode Reference
• Opcode Table
• Pan Docs
• more gbdev resources

How to add a new…

• Card (up to 254)
• Text
• Booster Pack
• Button on the Pause Menu
• Challenge Cup prize card
• Effect Function (various)

Port from Pokémon TCG 2

• Female character

Gameplay changes

• Adjust Weakness and Resistance Modifiers
• Create turn flags to limit retreating to once per turn and make new card effects
• Don't allow first turn attacks
• Update confusion mechanic

Improvements

• Add a duel shortcut for conceding a match
• Make AI be able to use attacks with any energy color combinations
• Remove AI artificial delay
• Save space and improve performance with RST vectors
• Speed up the duel animations of Drawing Cards, Shuffling Decks, Coin Toss, and Placing Prizes
• Speed up the start of the game (e.g. faster text speed, skip tutorial, etc.)

Miscellaneous

• Fix common text display glitches
• Replace damage counters with numbers to allow higher HP values (120 → 250)

To do

Feel free to contribute one of these!

• Add new:
  • card type (e.g. Darkness or Metal);
  • Auto-Deck Machine deck;
  • effect commands;
  • NPC duelist with custom deck;
  • coins (like in Pokémon TCG 2);
  • location in OW map;
  • status condition (Burn);
  • impossible cards (Electrode Lv. 40 and Ditto Lv. 20);
• Gameplay changes:
  • Implement the mulligan as an option;
  • Stadium/Supporter/Tool cards;
• Improvements: