testlevel chapters 2-31 overwrite game memory (coin counter and flag rows end after world 8: progress, language, options): level projects, play-tests and the arena use chapters 1 and 32-49, old settings migrate; level tally counts the level's own coins and secrets

docs/manual/01-introduction.md

@@ -76,7 +76,7 @@ created. Object types of other levels can be added later with **Assets → All w
 
 The game has eight worlds – **Village, Jungle at Night, River, Jungle by Day, Mountain, City,
 Catacombs, Lab** – each with several chapters. A ninth, hidden world called **TestLevel** has 49
-empty chapter slots. New levels go into one of these TestLevel chapters, so they never replace an
+empty chapter slots; 19 of them (1 and 32–49) are safe to use. New levels go into one of these TestLevel chapters, so they never replace an
 original level: each project gets its own chapter (shown in the New level dialog and in
 [Level settings](14-level-settings.md)). In the game they appear on the world-9 map as
 "TestLevel – chapter *n*".