This is a multi-part question.
1. Is the service itself legal? This website only describes how to play and shows the status of the lottery, it is not running the lottery. The actual lottery is using blockchain technology and does not need a website to work, so like bitcoin, no country has jurisdiction over the service.
2. Is it legal for me to play? Check your local laws for gambling and virtual currencies.
Yes. This was designed using blockchain so everyone has full visibility to all the information.
Blockchain is a software term describing a list of items where each one can not be changed after the next one is added. If you really care, you should at least read the first two paragraphs on Wikipedia. SuperLottery uses this for game details, tickets purchased, winner calculations, and payouts. Everyone can verify that the winners and payouts are exactly what you expect.
You don't have to understand blockchain to play, you can trust that enough other people are able to verify the game is safe.
Buy a ticket and you will be entered in the lottery. When the game ends you will be automatically paid back out to that same account if you win. You don't even have to remember your ticket. It's that easy.
Each new game is a fresh start. The total pot is the total of the tickets purchased. Picks are two numbers, 1 to 10. If you get the first number right, you get a "small" win. If you get both right, you get a "big" win. For example: if there are 100 players at 10/ticket, the pot is 1000. If 10 people get the small win and 1 gets the big win, the 10 small get 1 point each = 10, 1 big gets 10 times as many points = 10, total = 20. 1000/20 = 50. 10 small winners get 50 each, and 1 big winner gets 50x10 = 500. (The 1% rake is taken out of the example for simplicity)
Basically, If you win small, you get 5x, if you win big, you get 50x.
This can change in a lot of ways.
When the game is over, a "final block" will be added to the blockchain. The hash of the final block will determine the winning numbers. This value is unpredictable during the time tickets are being purchased.