Essentially, the online wallet service hold the private keys for you and perform the transaction for you. You only put trust on them and them actually hold the bitcoin for you. In the case if the service goes down, you lose all you bitcoin with it.
Start learning how to generate a paper wallet or purchase a hardware wallet if you are interested to store your bitcoin long term...
first thing you should improve in hte site is a different color for the result of your gamble, now all even you lose or win are showed as red, this should be differentiated, it would make gambler life easier(in my opinion thats mandatory, the change i mean)
it is red if you lose
and
it is green if you win
I suppose the OP meant, no matter what, you lose...