Fun reaction game. You have to click the gems as they appear on the screen before they either disappear or get eaten by the bad guy. If you miss more than 10, the game is over. If you catch a cyan gem you get 5 points, a green gem gives you 1 "miss" bonus, a red gem resets your missed gems to 0. Beware tho! If the monster catch a cyan gem your missed will increase by 1 only green and red gem increase it by 2 and 5!
Just click the gems with left mouse button before they disappear, quite easy to play!