Design for simplified poker with few elements

I'm doing my first front-end web project: a little poker hand calculator [you have the cards in your hands, physically, and you have a computer/phone to calculate the bets.

I'd like to keep things to a minimum, the poker table, and the action buttons [fold/follow etc]. for now, I have a slider for the bet, I wonder if there's a better/simpler way.

Since I don't have many elements on the page, it feels "empty" and cold, I don't know where to put things, what colors to put them in, etc etc.

Any tips at any level appreciated !

Also, I'd like to do the same thing for computer/phone. Is that possible? [I don't know much css, but I figured if I do everything in % it should render well on both? Will I need @media to specify things?

Here is the github link of the project. It's far from done.

I'm specifically talking about the "game" page, where the table is. (the rest does not matter for now]