Sandbox

Argument

Symbol key & formalization

Keyboard controls

Rules ⇄ has proof commands; Symbols ⇄ has formulas. Swipe left for Rules or right for Symbols. Scroll the keys for more.

Numbers stay along the top. Use Space between citations. Rule keys add their own spacing. Add submits your command.

Tap the text to position the cursor. ⌫ deletes text; keyboard Undo undoes typing. Undo beside the command box removes a proof step.

ABC opens your phone keyboard. Tap Logic to return. Hide ↓ clears the keyboard so you can read the proof.

Premises Conclusion

System Premises Conclusion

Disabled rules:

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Your current unfinished work will be cleared. Completed exercise credit is kept.

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Progress settings

This permanently clears your exercise results, XP, streaks, unfinished work, and skill check. Your account and challenge records stay.

This cannot be undone.

Symbol reminder

Letters take their meaning from the key in each exercise.