this is an interesting concept for a game, and it looks and sounds good. my main suggestion would be to give the player a clearer reason for picking one card over the other. i'm wondering if there's a way to change the odds based on the type of card you play; e.g., picking a higher card might increase the number of coins you can flip, giving you better odds (with two coins against one [medium card vs low card], there would be an 87.5% chance of winning or tying, but with two coins against three [medium vs high], the odds of winning or tying drop to 50%). assuming my math is correct :-)
one other suggestion: on my browser the whole viewport moves slightly when the cursor moves. this effect is a bit jarring.
overall, i think this has the potential to be a really fun game combining strategy and luck!