The game itself might be exciting for users, of course, and I guess you accept payments in Bitcoin, right?
It should be. The op should also accept bitcoin as one of the payments.
They are considered scam pretty much automatically. So if it's a Ponzi, you probably shouldn't advertise it (come on, even Wikipedia's definition of HYIP says it's a scam), and if it's now what you meant, you should explain yourself more, I guess.
I won't take much time to involved myself in this game because it's HYIP and we all know that it's a pyramid scheme or ponzi scheme which is not a great start. I guess the op won't explain more if the players are paid in the way that HYIP (Paid with the money of other investor's investment) would.