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PlugBrain vs Opal: catalog facts
PlugBrain	Opal
Free Free and open source under the GPL-3.0 licence.	Freemium Free to download, with a paid Opal Pro subscription for more features.
Android	macOS, Android, iOS
Math challenges add friction instead of a hard block Difficulty adapts to how often you open the apps	App blocking rules that apply on phone and desktop Focus timer that locks apps until it runs out
Android only No releases published on the GitHub repository	Some features require the paid Pro subscription Gamified rewards and friend invites may not suit everyone
Downloadable app	Downloadable app
Open source	Closed source
License: GPL-3.0	License not stated
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.