Rainbow Gun

The Rainbow Gun is a Hardmode, post-Plantera magic weapon. It launches a rainbow that travels in a straight line for a short distance before curving downwards. The rainbow persists for 40 seconds or until another rainbow is fired. Enemies touching it take damage repeatedly, approximately five times per second. The Rainbow Gun is found in the Dungeon's Hallowed Chest, which must be unlocked with a Hallowed Key.

Physics

 * Fired horizontally, the rainbow will travel straight for approximately 35 tiles before curving.
 * Fired 45 degrees, diagonally, the rainbow will travel approximately 4 tiles before curving.
 * Fired at a perfect 90-degree angle up or down, the rainbow will travel straight for 1491 tiles and end abruptly after that, due to the 20 seconds limit of the projectile.

Tips

 * The Rainbow Gun is a convenient weapon that pierces infinitely and delivers its damage repeatedly and rapidly without having to re-fire for 40 seconds. Large clusters of enemies, even post-Plantera Dungeon enemies (with the exception of Paladin and bosses), can be defeated all at once with a single firing.
 * This weapon will pierce infinitely until it fades. Therefore, it is a great weapon against enemies with multiple segments, especially worm-like enemies such as The Destroyer. It will hit each section simultaneously, inflicting tremendous damage. Because of this, it is potentially possible to defeat the Eater of Worlds or even The Destroyer with a single shot, if the player has appropriate gear and has made other preparations.
 * The Rainbow Gun is also exceptionally powerful against walking creatures or teleporting creatures. In the Hardmode post-Plantera Dungeon, while aiming towards the only passage leading into the room, the player can lay down a rainbow that eliminates every enemy that enters beside the occasional Cursed Skull or Paladin.
 * For the same reasons, the weapon is exceptionally potent against invasions.
 * Because of its high sell price, the Rainbow Gun is very expensive to reforge. It may be wise to settle for a lesser modifier such as Mythical, Godly, Demonic, or Masterful, all of which are equally damaging as long as the Rainbow Gun is not the currently-selected weapon.
 * Since the critical strike chance of a projectile is based on the weapon currently held by the player, this weapon pairs well with Stellar Tune and Staff of Earth since it will benefit from their high base critical strike chance.

Trivia

 * The Rainbow Gun can be used to bounce a Beach Ball, allowing a high bounce score.
 * The rainbow makes a faint light that is synchronized with other rainbow items such as the Disco Ball and Rainbow Bricks.
 * The Rainbow Gun is the only Biome Chest weapon that has a specific associated achievement.
 * The Rainbow Gun's projectile can travel up to 2,985 blocks vertically before stopping.