wow
W00t!!!!!!! this IS the best game on newgrounds. Its just like Metal Gear Solid! I'm a huge fan of MGS game Finaly a game im good at! Those last 3 levels were as hard as hell though, mission 19 is defidently the hardest.
In mission 20 first you must put the barrel on the floor button, go outside and knock on the north side of the pillar type wall, then quickly plant a bomb by the box, don't detanate the C4 yet. After you have placed the C4 quicly hide in the grass before the guard returns to his post. then knock on the north west part of the same wall and go in the north building. Hit the switch and wait for the guard to come back. Detanate the bomb now, the guard will be distracted and the box will be destroyed. while the guard goes to investegate go south of the place where you planted the bomb and press up agenst the wall. While the guard heads back again go in the eastern room and enable the switch. move to the door way of the building and knock on the wall, the guard will come then hide in the southeast part of the room. AS SOON as the guard turns around run out the room and go south, with any luck you will have made it past the hard part.
Go back in the building and knock on the wall opisite the guard in the exit door way. then when his is on the move just go in the doorway and congradulations!!! You have unlocked the bonus level!