Select controller:- Stage Start
After pressing start, you'll drop onto a highway. Now is the time to start practicing your rapid shot. Press 
to As you make your way right, you'll notice cars driving past - some of them are in pretty bad condition. Immediately after, you'll face your first enemy: a rolling spiked wheel.
After the wheel, there's a missile guy. Jump the gap, then get ready to face several flying enemies that carry spikes underneath. When you destroy them, they drop their spikes. If the spikes land on a part of the highway that is vulnerable, it will destroy it. You'll notice that if enough of the highway breaks away, a gap can be created. Also notice that the only breakable parts are between the poles that support the highway. The sprites for those sections (they are square and sometimes have a street lamp on them) are invulnerable, so if you time your kills correctly you won't have to worry about falling or jumping around uneven terrain.
Sub-bosses: B-Bladers
Just continue, making sure to kill everything ahead of you. You'll then face off against a giant mechanical bee, which is called a B-Blader; simply run to the left side, then short hop and fire charged shots until it dies. The highway will cave in under you, so you'll have to wall climb the right side to get back up. You can also pick up some energy capsules by jumping down into the next pit.
Continue on and you'll face some walkers (they only take two shots, so just make sure you hop to get them quickly) and another B-Blader. This time, it will spawn walker enemies to fight you, so take it out before the walkers can reach you.
Mid-level
As you walk in this next section, parts of the highway will start smoking and then fall out from under you. They are easy to recognize, being a different color and often being in the form of a single piece of highway hanging off the edge. Oddly enough, you can wall climb them without them falling apart.
You'll come across two more types of flying enemies. The first is a wasp like robot that just flies horizontally, the other is purple and similar in appearance to the robots with the spikes underneath. These purple enemies are slow, but will follow you around. They don't shoot anything so take the time to blast them while they appear. The way they are programmed is such that when they appear on screen, they will fly towards a designated spot, then wait a moment before attacking you.
Fun with vehicles
The last type of enemy you'll come across is a robot driving a car. Just fire quickly and you'll blow off the robot, but the car he was driving will still be running. You can jump onto the car and ride it, but make sure it's going in the right direction! The cars can only turn if there is a robot driving them (jump over one, wait for it to turn, then kill the robot and ride it if you want).
When you come to the long flat stretch with lots of cars, you'll see a massive ship floating above you dropping them from a loading dock. Run to the far right edge where the screen ends, and just take out cars while you wait. After destroying around four or five cars, the boss will come after you.
Boss: Vile in Mech Armor
This is a storyline battle, so you can't "win" (Vile is invincible). Once your energy meter drops below a certain point (around four energy bars), Vile will start shooting "energy nets" (glowing yellow orbs) at you. If you get hit by one of these projectiles you'll be trapped and both the fight and the level will end with a short cutscene. Keep in mind that if you're hit enough times before being trapped by one of the glowing orbs you can still die; so to fight against this boss well safely, just let one of the orbs hit you.
Password thus far
Your reward for finishing the stage is the first password of the game, which will let you bypass the Highway Stage if you enter it from the main menu. Each time you complete a level, collect a permanent item, or acquire an upgrade the password will change.