Think you could add a snap-to-grid type function? The spacebar vertical change is great, but it can be difficult finding the exact height to squeeze a piece into. Lesser but same for horizontal placement.
You make some new and interesting mechanics in your games. Can't wait to see the next one, and when you ever get around to some grand collection of all these mechanics in one game. Maybe something like a modern retake on "Gauntlet" (or a single player game cool too).
Make pieces easier to remove. There's one puzzle with three vertical red corners and once I place a piece it will not give me an X to remove it (the top right piece with the arrow)
Would be useful on the spike levels if they flashed yellow when they were one step away from red. When raising a block I don't know I've hit the fall limit until it's too late.
Oh no! Have you disabled cookies? That's how the game saves your progress, and it's saved every time you beat a level. (But I'll let you in on a little secret: to unlock all the levels, inspect element, inspect the game area, go to the console, and type "unlockAll()" without the quotation marks. Hope this helps!)
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 "Fusion"){kind=icon}
 "Choppy Orc"){kind=icon}
 "World of Talesworth"){kind=icon}
 "Logicheck"){kind=icon}
 "One Trick Mage"){kind=icon}
 "Ambidextrous 0"){kind=icon}
 "World of Shapes"){kind=icon}
 "Rotate"){kind=icon}
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 "The Man Who Can't Jump"){kind=icon}
Yeah, I knew I wanted to do something different, rather than rehash the same mechanic again.