Loved this game. My criticism was going to be the lack of drawback to mindlessly ignoring chains while preparing a big combo, but then I saw your comment saying that failed combos increase Speed. So it's cool to see you've thought of it, but I also didn't notice the drawback. You could maybe flip it to a temporary speed loss for the player, like a tummy ache from mixing weird flavors or something like that to be thematic, instant, and noticeable. Barring that, just make the vending machine and Speed number flash red when you whiff a combo or something
Got a score of 568,600 on 00 normal and 48,000 on 10 hard
That Normal game did feel a bit drawn out, especially in the beginning as I was figuring it out, but getting that one 102,400 popup was a pretty fantastic feeling and I got nowhere close on Hard. In contrast it was a little disappointing having lower-number chains not really do much, it doesn't seem worth going for them rather than just getting repeated 1chains while stocking up your main snack. Maybe you could have a longer Stamina bar, and higher chains refill more of it? But something like a 4chain would start to max it out every time.
That and the above speed loss for whiffing would kind of flip it so chaining gameplay is the survival gameplay and scorelets would be encouraged to engage with it, much like Radiant Silvergun levels up your weapons for chaining properly.
I'm going back in for a 00 Hard run with new tactics in mind