Edit: If the game seems laggy, play it in the popup instead of in the same browser.
Your goal is to find the lost baby penguins and bring them up to the surface. Peng will follow your mouse, clicking will cause two things to happen: A stun where your cursor is, and peng will perform a spinning attack at the same time. Moving the screen is done with WASD but can be changed in the settings or even set to move with the mouse if you prefer. Settings and a map can be found in the menu accessible anytime during gameplay by pressing Z. Holding space will make peng stay where he is and shift will make the baby penguins stay where they are. That should be enough info if you don't feel like following the tutorial.