Pause menu opens with Esc!
The point of the game is to remove all of the “numbers” or “tiles” or whatever you call them. You can remove numbers that are equal or sum up 10. They also must be adjacent: either left-right, up-down, also the top tile of a row and the bottom tile of a row, and the last and first tile. When you think you have no more moves, or just want some more tiles click “More Tiles” which will copy each and every tile on the board and add them to the end of the row.
If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).