Golden Euro Casino has become the latest online casino to offer the 25-payline Secret Symbol slot from developer RealTime Gaming and is this week celebrating by offering players a special surprise bonus.Featuring Aztec-themed jewelry and cultural artifacts on its five reels, Secret Symbol will award players that collect three pyramid scatter symbols with a free spins feature where wins can be multiplied by up to 20 times.“This week we’ll be sending players a secret surprise bonus by e-mail [and] it will give them extra cash to play with but they’ll have to claim their secret bonus to find out just how much they get,” said Robert Miller from Golden Euro Casino.