^^
No matter how experienced in trading you are, it's almost impossible to predict what the price would be or whether it will go up or down in the next 15 or 30 seconds. First because the difference between the starting price and the ending price is almost negligible and second because 15 or even 30 seconds isn't enough to analyze the market.
As you said, it's a luck based game so just enjoy it.
I don't really think it mainly base on luck there's still need of some analysis in order to get a higher chance of winning though luck may have a role here but it's not the basic.
Though entirely it kind be seen as a fun prediction of bitcoin price.
Also Op please, is there any chance of adding other third-party aside Changely, which may accept lesser minimum deposit with other crypto.
The type of trader that could be able to handle out this kind of movement or someone who could put up some analysis into this kind of price movement is into those scalpers
but generally speaking about 15 seconds or 30 seconds time frame is really something that no analysis that could really be applied.
Here are some of my suggestions;
1. Possible application of technical indicators 2-3 atleast

2. Smooth movement animation (i dont know if its just me or all people who do visit out the site)
3. Dark mode?
The site is fancy looking and really love those color combinations but sometimes it does hurt my eye too much.
In overall this one is really that something good if we do speak about binary options kind of game or gambling.