Clash at Demonhead/Route 14

Highlights

 * There is a small cavern hidden below the section where a letter drops, which contains an invisible enemy along with several hearts.

Description
Assuming you entered this route from the right side, clear away the slow high-bouncing enemies, and proceed to the left. A few lower bouncing enemies will approach you as you climb over the gray blocks. When you reach a gap in the ground, a letter on a parachute will drop down. Collect it to read it. Someone named Jake has sent you money ($10,000), and claims he'll take care of your girlfriend for you while your gone, which makes you more worried. At this point, if you drop down through the bottom of the screen, you'll enter a room which contains three hearts and an invisible enemy. It's possible to detect the enemy's location by watching where it shoots from and fire at it to remove it. You can leave and return to collect as many hearts as you like.

Continuing on to the left, you'll eventually reach a body of water with platforms above. You have a couple of choices when it comes to crossing the water. You can try to jump along the platforms, some of which contain gold, but there are looping enemies that pass through here, and if they collide with you, they will likely push you off. You can put on a Jet Pack and simply fly over everything. Or you can swim, but when you reach the right side, the ledge will be too high to jump up to. The only way to reach it from the water is if you have a Jet Pack that you can use to fly up.

Game walkthrough
From here, you're only option is to continue on to.