If you download the demo, you can play through the full single player game if you do the following:
Begin playing, and when they "Buy Now" popup happens about midway through the first level, just hit the start button. It bring up the pause menu, and when you unpause, you resume playing like nothing happened.
Begin playing, and when they "Buy Now" popup happens about midway through the first level, just hit the start button. It bring up the pause menu, and when you unpause, you resume playing like nothing happened.