There are three paths to take from the beginning of the game, you simply found one of them.
Don't try reaching the ledge on the right while falling. Instead, fall straight down. You should one of the spikes from the left spiker wall shake. Shoot that spike, and use your second jump. The spike should fall down, serving as a platform, and you should land on it.
Soon, blocks should appear out of nowhere(*ahem* Megaman), you jump on them to reach the ledge.
To beat the entire game, you have to take all three paths from the beginning. When you get far enough in one path, you are offered a teleport back to the start.
Hi by the way.

First post!