[ second swap rows>> nth ] keep first swap ;
: set-block ( board block colour -- ) -rot board@block set-nth ;
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+
: block ( board block -- colour ) board@block nth ;
: block-free? ( board block -- ? ) block not ;
#! remove full rows, then add blank ones at the top, returning the number
#! of rows removed (and added)
remove-full-rows dup height>> over rows>> length - swap top-up-rows ;
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