If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
Collect the droplets of Voltarol to pass to the next level. Encase the enemy in a bubble for a short time, shooting him the gel that you find.
Left / Right Arrow Keys - Move.
Up Arrow Key - Jump / Climb Up.
Down Arrow Key - Duck / Climb Down.
Spacebar - Shoot.