MD and PH warmup/RPS/C4

I think this method broke my brain. 
[@playfield, @playfield.map(&:reverse)].inject([]) <= woah. 
((-matrix.count + 1)..matrix.first.count).each <= double woah. I read this as "negative matrix dot count plus one, to the first item in matrix, dot count, dot each". It seems like #downto() would simplify this somewhat? Maybe not.
(matrix.count).times <= triple woah.  
This is very hard to read. I think everyone had trouble with those diags.