Toward Post-Game Reflection in In-Person Collectible Card Games: Match Reconstruction Using Chest-Mounted Cameras

Toward Post-Game Reflection in In-Person Collectible Card Games: Match Reconstruction Using Chest-Mounted Cameras Michihiro Niijima and Satoshi Nakamura Meiji University, Japan Card images: ©1995–2026 Nintendo/Creatures Inc./GAME FREAK inc.

Background Post-game reflection helps players improve [Wallner et al., 2021] Chess Fighting games Team-based games Street Fighter 6 League of Legends Reflect on past decisions to find ways to improve. G. Wallner, M. van Wijland, R. Bernhaupt, and S. Kriglstein. “What Players Want: Information Needs of Players on Post-Game Visualizations.” CHI 2021 Images: Aaaatu / CC BY-SA 4.0; ©Pokémon; ©CAPCOM; ©Riot Games 1

Background Post-game discussion in games like Chess and CCG Why did you choose this move? What else could you have done? To discuss player choices, player need to recall the situation. 2

Background Collectible Card Games (CCG) Post-game reflection is also important for improving play in CCG. Card images: ©1995–2026 Nintendo/Creatures Inc./GAME FREAK inc. © Wizards of the Coast LLC. Magic: The Gathering is a trademark of Wizards of the Coast LLC. 3

Background Chess and CCG: who knows what? Chess CCG Perfect information game Imperfect information game Easy Difficult 4

Background Chess and CCG: who knows what? CCG Chess Both players see every piece shared board Both players can reflect on their decisions using the same board position. Perfect information game Imperfect information game Easy 5

Background Chess and CCG: who knows what? Chess CCG Only the owner sees the hand opponent’s hand is hidden If a player cannot remember their hand, their opponent cannot know what cards they hand. Perfect information game Imperfect information game Difficult 6

Background Chess and CCG: who knows what? Chess CCG Only the owner sees the hand opponent’s hand is hidden To support post-game reflection in CCG, we need to record matches including players’ hands. If a player cannot remember their hand, their opponent cannot know what cards they had Perfect information game Imperfect information game Difficult 7

Camera position and hand visibility [Fukushima+ 2025] Overhead camera Recording with an overhead camera Hand Play area We need a viewpoint that can capture the cards in the hand. 福島颯太，宮本友樹，片上大輔：TCGにおけるリアルタイム自動実況システムの開発，HAIシンポジウム 2025 8

Chest-Mounted Cameras A smartphone on each player’s chest Camera position What the camera sees The hand faces its owner. A chest view can capture it with the play area. Card images: ©1995–2026 Nintendo/Creatures Inc./GAME FREAK inc. 9

Overview of our system Card images: ©1995–2026 Nintendo/Creatures Inc./GAME FREAK inc. 10

Card detection Card images: ©1995–2026 Nintendo/Creatures Inc./GAME FREAK inc. 11

Event estimation Energy attachment Switch Card images: ©1995–2026 Nintendo/Creatures Inc./GAME FREAK inc. 12

Match log generation Card images: ©1995–2026 Nintendo/Creatures Inc./GAME FREAK inc. 13

Pilot study 2 evaluation metrics ①Card detection ②Action detection 15 matches First author and 5 collaborators 3 matches with each collaborator Both players recorded video 14

Pilot study: Result① Card detection Comparison with records made by hand 500 frames for card detection Successful card Target F1 Hand cards 0.91 Play-area cards 0.85 Missed card 15

Pilot study: Result② Action detection View point Author Collaborators Event (F1) 0.47 Author 0.70 Collaborator 16

A small study of post-game discussion 3 pairs 2 matches per pair How did using the log change the discussion? Card images: ©1995–2026 Nintendo/Creatures Inc./GAME FREAK inc. 17

Three changes in post-game discussion 1 More specific choices A general idea for a better move became a plan using a specific card. 2 Reasons behind the opponent’s play Players checked the opponent’s hand and discussed why they chose an action. 3 Links to other moments One situation led to discussion of related moments before and after it. Card images: ©1995–2026 Nintendo/Creatures Inc./GAME FREAK inc. 18

Future work More reliable logs Improve camera positioning and reduce missed events. Test with more players and a wider range of decks. Learning from discussion Examine how logs support post-game reflection. Test whether these discussions help players improve their play. 19