It adds a new mode which introduces "bonus powerups" from the first game of a streak (these are difficulty modifiers that would previously only show up after winning a few games in a row), with 8 more powerups added to the 12 from the original, so there's more variety from the start. Also 9 new progs (for a total of 32).
These changes make the score of an individual run less meaningful - because it's always affected by random powerups and because some of the new progs interact with run streaks - so high scores in this mode are only for streaks (total score across a series of consecutive plays without dying).
The maximum number of progs held is dropped to 8 (from 10), which makes the choice of what to pick up a little tighter, and also adds a little more variety because you're less likely to be able to pick up the same combinations by the end of a game. The new mode also allows a choice of "character class" each game, which determines starting resources (previously this was randomly assigned); this choice gives an extra chance to respond to the random initial conditions so there are less "unfair" deaths at the start of a game.
There are a few minor changes to some of the original progs, mostly to clarify their interactions with the .PLAN.B metaprog which executes random other progs: it was annoying to have it repeatedly apply an unwanted effect when you were hoping to randomly trigger something specific. In particular .DELAY and .STEP can no longer be used repeatedly in the same turn - you can still .STEP across a distance by applying it after each move so it isn't any weaker; .DELAY is slightly weakened but it was very strong in the first place so that's okay. Some other progs could be used with no effect when there were invisible cryptogs around, on the grounds that you don't know where they are so maybe it's affecting them - even though in practice you often have enough information about their position that you might know; now these can only be used when they will definitely have an effect, so their availability might give a clue about a cryptog's position (e.g. .CRASH becoming available might tell you there's one diagonal to you). I think it's quite interesting to get these clues and I'm not at all sure why I ruled them out in the first place?
ok set a good score now. i should release this? pic.twitter.com/ftiqkRuFZD— Michael Brough (@smestorp) June 13, 2017