Thanks for the feedback - I really like the suggestion for mouse-based throttling since I wasn't sure how to give more fine-grained speed control with the current control scheme. It didn't occur to me to have moving as the default either.
The shape thing does need some work, I've been trying to tweak it but it gets kind of biased in what is considered a "good" shape and I had trouble making it more lenient without it accepting shapes too readily. Short-term I can probably adjust the thresholds for the more complex symbols, but I think I will need to look more into the handwriting recognition literature. I've also experienced the pain points of losing momentum, so I will have to figure something out there too.
Time shifting requires that you have some time meter (indicated by the spinning shell) which you get by destroying enemies, and it gets stronger the more you have stored. As a visual indicator there should be kind of a fog that appears when you use it that scales with the strength of the slowing.
Hopefully I can address some points before the submission period ends