A nice Heboris Item Mode playthrough.

In this mode, every so often you will be given an item block. Some are positive, some are negative, some are context-dependent, and some literally do nothing (because there is no second player to swap the board with). Things in this mode do get pretty random, cause one run you can get a lot of nice, calm things with minor effects on actual gameplay, and other times you can get Shotgun (adds stupid amount of holes into your stack) followed by Nega Field (replaces holes with blocks and blocks with holes for every line of your field) leaving you to just pray for some line clearing effect or Cascade.

That being said, you can often pick what you want to get - the items spawn often enough that you can relatively easily have two of them on the board, and when you activate one of them, the other one will disappear. For example, you can skip getting a Death Block (big piece) by waiting till the next item, which may for example be Boost Fire (forces max gravity for a few pieces). Granted, sometimes it does make for some very awkward stacking, but it is a very useful tool to keep your stack clean.

And when it comes to keeping your stack clean - well, you still have to clear tetrises to get the necessary score for the GM grade. The grading system in Master-#G1 is roughly based on the TGM1's grading system - however it is rebalanced for back to backs, hold, and three previews, forcing you to push stack cleanliness more than you would initially expect.