You could drop the shapes around the numbers, took me a while to realize 1 was 1 and not warning. Think the one around the 5 would work nicely for all.
The area where you make the eq. you could have the slots marked as the shape of the number tiles with appropriate color (and rainbow if any color).
The progression was a bit too fast. Introduce a new "trick" in easy way, Let player test it once or twice. Then mix it up or combine with previously introduced concepts. Then next trick.
The scoring, I think you should give the unused seconds on each equation to the user as a score. That way even if you only manage 1+2=3 you can still replay and improve.
So don't take these comments the wrong way, they're just suggestions and ideas. I kind of liked the game.