I think this is a great concept! You might be missing out on players by not having a web build?
Some feedback I have: As a colour-blind player I found it very difficult to see the different colours, could you add some shapes to help the player? Also I'd totally forgotten Red/Blue/Yellow are the primary colours, so used to RGB! One other thing would be to have the timer count up (high scores), instead of the stress of counting down. :)
Overall, good start and I hope you continue to develop it. 👍