This is excellent! Very simple set of mechanics, which led to a very deep experience - each new concept was introduced clearly, then explored thoroughly in the levels which followed. The interplay between bubble types in the later stages was great.
The game controls well, and I particularly liked the dash, which felt snappy and highly responsive. I thought it was a very nice touch to include the skip level function - I'll admit I needed it for one of the later stages, and was grateful for it's inclusion.