Blue

Blue is an enzyme and the main character of the Test Subject series. Blue is also called Test Subject Blue, or Test No. 0001232423545 by the professor. Blue also appears as an boss in the game Nitrome Must Die.

Appearance
Blue is a blue enzyme with two black eyes. Unlike other enzymes, Blue takes the shape of a teardrop.

Test Subject Blue
Blue started off as an experiment by the professor in Test Subject Blue. He put Blue through twenty-five tests, trying to see what the enzyme was capable of.

Test Subject Green
From the newly created green enzyme, the professor tested it out against Blue. When carrying out the third test, the sirens within the lab went off and the professor abruptly disappeared. Blue managed to complete this test and the professor tried to carry out the next, but lost hold of Blue as he injected him into the start cylinder.

Once Blue approached the food pill, it was snatched by Doctor Nastidious and taken to Doctor Nastidious' base.

Test Subject Blue, Green, and Complete
Blue appears as the main character in the series. It is the only playable character. The player controls Blue with the arrow keys to move and the space bar to shoot a proton bullet. Pressing the left or right arrow key will move Blue left or right, respectively. Pressing the down arrow key will cause Blue to crouch, and pressing the up arrow key will cause Blue to jump. Normally, Blue can only walk on the top of platforms. However, in Test Subject Complete, Blue can walk on the bottom of platforms as well. If Blue comes in contact with a hazard or an enemy, then it will die and respawn in the most recently activated spawn cylinder.

In order to complete a level in Test Subject Blue, Test Subject Green, and levels one to six of Test Subject Complete, the player must move Blue first towards the key card of the level. The key card will then open up the food pill container upon being obtained. Then, the player must move Blue to the food pill, which will allow the player to progress to the next level upon being obtained.

However, in levels seven to twenty-five of Test Subject Complete, the level objective is different. In level seven, the player must make Blue shoot the mercenary's hand in order to escape the test chamber. In levels eight to twenty-five, the player must move Blue to the transporter of the level in order to complete the level.

Test Subject Arena
Blue also makes an appearance in the spin-off Test Subject Arena, facing off against Green from the sequel. The spin-off introduces a new melee attack where when it can attack Green within a very close range. Instead of shooting with the proton gun, Blue will slash Green with an extended piece of its gun. Blue acts exactly as he does in the Test Subject games.

Test Subject Arena 2
Blue appears in Test Subject Arena 2, retaining his exact behaviour from Test Subject Arena.

Nitrome Must Die
Blue appears in Nitrome Must Die as the fourth boss of the game. Blue is held by the professor, whose hand is reaching out of the wall. He will move the enzyme in its suit vertically up and down the wall.

Phase one
Blue attacks by simply firing its gun while the professor moves it up and down. After having its health lowered down to a certain point (but less than half), it will strike a pose it does when it gains a kill in Test Subject Arena and cause several giant blue spheres to appear, all which will try to home in on the player.

To increase chances of survival, firing the weapon (containing bullets) destroys the blast, leaving the player's character unharmed. (This strategy of firing at projectile to avoid damage also becomes useful during the fight against the final boss.)

Phase two
After lowering Blue's health down to slightly less than half, it will switch into the Rex209 and fire more rapidly. Blue will continue to fire green proton bullets continuously while it on the screen, only stopping when it is pulled back off the screen.

After Blue's health is depleted, the hand will move vertically up and down, then explode. After a few seconds, it will fall and be slowly pulled off the screen.

Proto-suit
In the first two games of the Test Subject series, Test Subject Blue and Test Subject Green, Blue performs its tests in a mechanical suit known as the proto-suit. The proto-suit was designed by the professor. The suit allows Blue to shoot proton bullets for defense, and move freely around its surroundings. Blue is also given the ability to jump when hazards are presents. Hazards will instantly shatter and destroy Blue's suit, as well as Blue itself.

In Test Subject Arena, the suit also has a special melee attack. When close to Green, the suit will slash the enzyme with an piece of proton extending from Blue's gun. Also, when Blue kills Green in Test Subject Arena, the suit extends a portion of a proton from the top of the gun and strikes a pose, pointing the gun upwards.

Rex209
In the game Test Subject Complete, Blue is removed from the proto-suit and is placed inside a new mechanical suit, Rex209. Rex209 was designed by Doctor Nastidious. Rex209 has all of the capabilities of the proto-suit (except for the melee attack), plus some extra features. First, the proton bullets that Rex209 shoots are more powerful, and can kill enemies quicker. Also, Rex209 has the ability to walk on the bottom of platforms. If the Rex209 suit is destroyed, then it will break apart into several pieces of metal and glass. The suit will then reassemble at the last spawn area that was activated or at the beginning of the level if no spawn areas were activated.

Occupation
In the Test Subject series, Blue's occupation is being the test subject of two people - the professor and Doctor Nastidious. In each test, Blue is spawned and placed in its suit by a spawn cylinder. In each level, Blue must navigate itself to a food pill, which at the start of each level is surrounded by a glass capsule.

To deactivate the glass capsule, a key card will must be obtained. Blue can now obtain the food pill, which Blue will pick up when it gets near the food pill. Blue will then be sucked up by a syringe to be transported to the next level. Blue may have to use other objects to get to the key card and food pill. Also, while accomplishing these tasks, Blue must avoid all enemies and hazards, or else Blue will die and respawn.

Other appearances

 * Knight Trap/Office Trap/Nitrome Must Die - Blue cameos as an enemy called a slime in the Trap series. This slime will jump across a platform forever.  The blue slimes also appear as enemies in Nitrome Must Die.
 * Nitrome 2.0 skin - Blue appears above a vat of orange enzymes.
 * Avalanche skin - Blue appears running away from an avalanche.

Trivia

 * When Blue stands in one place for a set amount of time, it will throw itself up against the glass in its suit twice, creating cracks, which will quickly disappear after Blue shakes its head.
 * Blue seems to be a rather advanced enzyme, as it is shown that he is capable of thought, memories, and emotions.
 * In Test Subject Arena, Blue gains a special melee attack where it will slash Green with a piece of proton extending from its gun. This melee attack has not been used in any other game in the Test Subject series.
 * Although enzymes don't have a gender, Blue is referred to be male in the Test Subject series.
 * Blue bears a strong resemblance to the main character in the video game Dragon Quest Heroes: Rocket Slime.
 * Blue slimes that look similar to Blue are seen in many Nitrome games, including Knight Trap, Office Trap, Nitrome Must Die, and Blast RPG.