10x Tough

The title says it all; a simple routine for some serious daily training. I set the range to 2500-2900 for now. That way, you don't know just how difficult the puzzle at hand is supposed to be. Might tweak number of puzzles / rating range or add a warm-up section in the future. E.g., if it turns out 10 puzzles takes too long, I might reduce it to 7 or 8.