Open the door in the roof and click on the "red dot" object to turn it into the green arrow. Click on the small yellow arrow beneath it to make the stickman walk right and fall through the hole, then click on the green arrow to turn it back into red. Click on the crate the to the right of the stick man to let out a grenade. Keep clicking on the little yellow arrow to make stickman throw the grenade up, which will then be blasted forward by the red dot. The grenade will fly into the door on the right side of the screen and blow it up, then click on the pink plank sitting right on top of the crate (where the grenade came from) until it falls off and makes a ramp. Click on the stickman to make him go through the door you just blew up. Open the window to scare the blob down to the ground.
After that, look at the top left side of the screen. Tilt the lamp and turn it on so that light shines on the balls. Click on the crow, which will pick up a ball and fly across the screen. Here is where you need timing: Click on the first cloud as the crow flies by to make it drop the ball on the antennae on the hill below. After that, click the blob to get it out of the way; it will go into the water.
Turn on the underground switch to make the light underneath the steps turn on, then click the blue arrow pointing right on the circular underground thing. This will make the "wheel" on the steps rotate clockwise. Click on the stairs to make it move to the right. Ring the doorbell to make stickman come out and climb onto the roof.
Click the crow again to pick up another ball, but click the second cloud this time as the crow passes by, making it drop the ball into the catapult. Once you click a cloud three times, it explodes on the third time. You have already clicked the first cloud once, so click it again. You will require timing again at this point. Click the first cloud for the third and final time to make it explode, then click on the stickman at the catapult as soon as you can. He will launch the ball, which will fly through the acid rain from the cloud and turn into a fireball, which will then destroy the banner.
Click on the man on the top floor of the castle on the left to make him fall to the lower floor. Timing here is once again vital: Click the door-thing underneath the stained-glass window to make a fly and another stickman come out, then simply keep clicking on the fan in the wall (there is a faint arrow pointing to it) to make the fly bug the other stickman. Once the fly passes through the fan, click the stickman on the right to let him walk safely underneath the suspended crate.
After that, click on the leftmost stickman to make him fall again and so that he is next to the lever. All levers will then have an accompanying stickman. Start with the bottom stickman: Click on the arrow below him to switch it from left to right. Once done, click on stickman to make the water flow to the right. Then, click the middle stickman to open the trapdoor. Finally, click the top stickman to release the suspended crate.
Timing is important here. A fish will come out of the box and fall into the water. Once the fish hits below stair level, click on the bigger underwater gate to let the fish flow by and get caught by the fisherman. Turn off the water current by clicking on the appropriate stickman, then click the fisherman, who will eat the fish and bounce up to the roof of the castle. Click on him when he is on top to light the first torch.
Now for the second torch, turn on the water current again so that it flows to the right. Click on the red dot to turn it into a green arrow again and click the small yellow button to make the stickman at the catapult go inside on the right. Open the window to make another blob come out, then click on the new blob to make it explode the underwater mine. Turn off water current (this might not be needed, but just in case). Click on the blue left arrow on the circular underground switch to make the wheel on the stairs turn counter-clockwise. Click on the stairs to move it next to the crate.
The final part requires more timing. Ring the doorbell to let stickman out. Click the crate when he is almost to the top of the stairs to make him fall into the crate. He will bust out of the crate in a monster truck. Click on the underwater gate in time to let the truck pass. Stickman will ditch the truck and climb into the castle to light the second torch. You can now flip both underground switches to activate the portal.