- Note: This walkthrough only entails how to defeat the "real" Robot Master, and get the Beat Letter.
This stage starts easy enough, with cowboy-style bots that fire bullets at you. Their shots are easy to dodge, and you can return fire easily enough. For the most part it's a straightforward level without a whole lot of confusion.
You'll encounter a Hard Hat dispenser about midway through the stage. It can be destroyed by shooting the small tube that actually dispenses the bots.
Following that battle, you'll find a ladder high in the sky, above your normal path. Fly up to it with the Rush Jet, and you can get some useful stuff, and avoid some challenges.
At one underground section, you'll have an option of two paths, high and low. You need the high path to get to the Energy Balancer item, and the low path to get to the real Robot Master with the Beat Letter.
Start by going high. On the screen immediately following the branching area, you'll find a ladder above a bed of spikes. Equip Rush Power and hang as low on the ladder as you can without falling off. Use fully-charged Rush Power to trash the cracked brick on your left. Go inside and get the Energy Balancer. Once you have it, backtrack to the fork in the road, or simply kill yourself to resume from the continue point.
Now go low, so you can reach the real Robot Master. The low path is straightforward, just destroy whoever gets in your way. Get through the "dropper" platform section in the next room over, and you'll find the Boss Room.
Tomahawk Man is one bad dude, and he's here to bring the Blue Bomber a whole new world of pain. He attacks with tomahawks as well as sharp feathers he fires from his head. Dodge his attacks the best you can, and hit him with the Plant Barrier. It's hard to hit with, but he's far weaker to it than anything else. Just keep bringing the pain, and if things get too hairy, use an Energy Tank.