Crazy Machines Elements

You'll first need to unlock the editor by solving the first five puzzles of the "Rigid Basics" pack in puzzle mode. See Perfect Puzzler if you need help with this. You'll also need to complete at least some of the puzzle packs to unlock the cannon and other useful parts, although it helps to just wait until you've unlocked Collector so you'll have everything at your disposal.

Start a new level in editor mode, and select the cannon from the inventory. You'll need to place two into the level. Press until the cannon is pointed as high up as it will go, and then set it down on the floor. Now press to angle the next cannon so it's pointing down again, and then use to flip the cannon and to automatically light its fuse. Place this cannon in the air to the left of the first cannon. Now get the metal board and place one under the second cannon so it won't fall to the floor and another directly to the left of the first cannon so it can't roll to the left. Next, rotate the board so that it's angled downwards from left to right, and place some to the right of the first cannon's barrel to form a ramp. Now rotate the board until it's completely vertical and place two to the right of the first cannon's barrel to form a wall. Make sure that one of them is to the right of the barrel so that the cannon can't roll in that direction either. Next, get a heater from the inventory and place it next to the first cannon's fuse. Then get a chip controlled power socket and place it next to the heater. Be sure to plug the heater into it! Now take a timer chip. Use to set the timer to 5 seconds and then place it next to the power socket. Finally, use a wire to connect the timer to the power socket.

Now start the machine. If you set it up correctly, the second cannon will fire and its ball will bounce off of the wall onto the ramp, and then roll into the first cannon. Then the timer will start the heater, lighting the first cannon's fuse and letting it fire both cannonballs.