Move mario and sonic at the same time, collect the keys and unlock the houses to get both mario and sonic in to there homes at once, although it may seem simple it gets harder as the game continues. Good idea to disable the sound for this game as it's very annoying.
Some of our games still uses flash, be sure to click on the square in the middle then click allow flash when asked by your browser. Your browser may ask you to enable flash for each game you play, just use the same method on those too.
Click on the link below which says "Go to the game..." to go straight to the game.