Thinking is a lightweight Minecraft Forge mod that rewards players for standing still and thinking. When a player goes AFK, the screen slowly fades to black and they start gaining experience points over time.
You can customize the mod behavior in-game:
/gamerule afkMaxXP # Maximum XP reward per interval
/gamerule afkSeconds # Seconds before AFK detection starts
/gamerule xpDelay # XP reward interval (seconds)