Click a word to mark/unmark it as an error
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This simulation provides an interactive environment for honing editing skills. A passage of English text is rendered as a 3D wall of word-blocks, each one silently flagged as correct or containing one of four real proofreading error types — typo, homophone confusion, subject–verb agreement break, or duplicated word. Click any block to mark it as a suspected error, then press Check Answers to reveal hits, misses and false alarms, scored with the same precision/recall and signal-detection (d′) statistics used to benchmark human proofreaders and automated spell-check QA.