Contra/Stages 1 - 3
 Stage 1
The first stage scrolls horizontally, and takes place in the jungle. As soon as you begin, soldiers appear to attack you from the right. You should immediately open fire in order to clear a path in front of you. Before the bridge, you will encounter a weapon sensor in the cliff wall, which contains the Laser gun. This is quickly followed by a capsule that flies overhead from left to right with the Spread gun. In general, beginners will want to collect the Spread gun, but experts may prefer to stick with the Laser gun due to the damage it can do. The famous bridge sequence occurs, with explosives taking out each part of the bridge as you cross them. The explosions can kill you, so you must make sure that your jumps clear the explosions as they happen. It's much better to fall into the water below then to time your jump incorrectly and get killed.
If you fall in the water, note that you can not jump while you are swimming. However, you can dive underwater. Diving prevents you from shooting your gun, but it also protects you from bullets. Be aware that you will resurface from diving after a set amount of time. Two wall turrets will appear from the cliff wall. Destroy them if you can, but don't stop moving unless you are in a safe place, and their removal would make your path substantially safer. There is a Fireball gun in the weapon sensor beyond. Don't collect it unless you have no other weapon.
Snipers hide behind the bushes that appear beyond the waterfall. Two cannons will also appear by rising up from out of the ground and fire straight ahead. Soldiers will continue to appear on the screen from the right, and shoot at you. They are easy to pick off if you proceed cautiously. You're actually safest if you run along the bottom of the screen. Firing upward with the Spread gun may help you to remove enemies before they even get a chance to shoot at you. Another wall turret will appear near a weapon sensor. This sensor will contain the Machine gun, which is good to collect if you've died and lost the Laser or Spread guns. Be sure to clear out the area around you before you advance close enough to the base entrance to cause the screen to stop scrolling.
At the end of the jungle, you will reach the gate that protects the entrance to the first base. There is a soldier at the top of the base that shoots down at you. Two defense cannons fire mortars down at the ground below, on either side of the gate. These mortars will hit anyone standing too close to the gate itself. Stay off the ground below and take out the soldier at the top first. Then concentrate your fire power on both cannons. One shot with a laser is enough to destroy one of the cannons. Only when both cannons have been destroyed should you drop down to the ground below and shoot the gate itself. Hit with enough firepower until the gate is overloaded and explodes. Then your player will jump through the destroyed gate and down a hole in the back which leads to the basement.
 Stage 2
The second stage takes place inside of a 3D maze constructed from the internal passages of an enemy base. There is a time limit in this stage, and you will lose a life if you do not clear it in 1 minute and 10 seconds. In each room of the base, there is a sealed nuclear power core which you must destroy in order to advance. If you try to advance before the core is destroyed, you will hit the high-voltage current and become temporarily paralyzed by the shock, leaving you vulnerable to attack. In most cases, the core is level with your gunfire when you are standing, but in one case, the core is low to the ground, and you must crouch to hit it. All of the enemies will be instantly killed once you destroyed the sealed power core, so focus most of your efforts on the core once it is exposed. Soldiers appear from the left and right along the back wall and shoot at you, while turrets appear from the walls in most rooms. You are safe from gunfire whenever you crouch along the floor.
Some soldiers will toss grenades at you, but more common are the rolling mines which get sent in your direction along the floor. The mines can be destroyed with enough shots before they reach you, but the grenades must be avoided entirely. Special weapons can be obtained by shooting the red soldiers that jump across the background. Only one red soldier appears per room. As you advance from one room to the next, you must pay attention to your location on the map at the top of the screen. When you reach the back wall, you must choose the direction which will advance you according to the map. For the first base, you must choose: right → right → left → left. The very last room contains a much larger seal which takes twice as much firepower to destroy as the others. When it is destroyed, there is a slight pause before the explosion creates a hole in the wall, giving you access to the core of the base.
 Stage 3
The third stage is a fixed 3D display, where the bottom of a waterfall is visible at the top of the screen. Two arrays of turrets flank either side of a set of four sensors. The turrets fire bullets in three directions, including straight down, with some intersection in the middle of the screen between both guns. The boss of the stage will appear as soon as the sensors are destroyed, whether the turrets are destroyed or not. So it is vital that you destroy both turrets before all four sensors are destroyed. Otherwise, you will have more threats to deal with than necessary.
When all of the sensors have been destroyed, the Ocular Fire boss will emerge. It moves left and right in the small chamber above the sensors and turrets. Every now and then, it shoots a ring of fire that descends to the bottom of the screen. The ring can be destroyed with your gun. When there is no threat of a ring, concentrate your fire at the boss itself. After striking it enough times with your weapon, it will explode. Then you will hear the victory theme and your player will ride one of the elevators on either side to the surface.