They mention such things as:
Reflex
Lessquick
Float
Which are helpful, but I'm trying to find a game like Reflex, that allows you to endlessly play on 1 difficulty until you want to speed it up slightly. Reflex is fine, but it accelerates too fast for me. It turns from challenging to impossible so fast that any real training or muscle memory development is impossible.
If there is a game like this out there please let me know.