Collection mechanic. I love collection mechanics in games! At the time of writing this, the game has 92 different cars and I've collected 84 of them. On the collection screen the developer uses the tagline “gotta build'em all. … in MWCF the developer has some timestamp check and displays the below message. Players lose all their current doughnuts, and in my case, added 50-some hours on all of my cars and shops. I wasn't mad about it. I actually thought it was funny. …

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Better freemium design | Motor World: Car Factory – Games Brief