Wonderful right the way through - it's a brilliant central mechanic, with the additional colour combinations introduced at a good pace that didn't feel overwhelming.
The art and animation is great, with tons of charm. Loved the particle effects from explosions, which added plenty of weight and juice but never felt overdone.
Soundtrack is great, and the sound design is spot on, with the
I loved the attention to detail, with things like the cursor changing colour to match the active combination just adding a lot of polish.
Made it to stage 10 - the loss screen is so sad :( I'm sorry I let the little plant guys down