StarTropics was an action-adventure video game released by Nintendo in 1990 for the NES. Unlike most of Nintendo's games, it was never released or intended to be released in Japan. It was released only in North America and Europe, although designed by Japanese designers living in the United States. It was produced, written and directed by Genyo Takeda of Nintendo Integrated Research & Development (which also developed the Punch-Out!! series). The game was added to the North American Virtual Console on January 7, 2008, and the PAL region's on January 11.

StarTropics was followed by a sequel entitled Zoda's Revenge: StarTropics II, released in 1994.

StarTropics is played from a 2D top-down perspective, similar to The Legend of Zelda's dungeon areas, and various role-playing video games on the NES (town/overworld areas); however, StarTropics is linear and has a constant storyline. The game is divided into a series of chapters through which the story progresses. In each chapter, Mike initially walks around towns or other areas, talking to non-player characters and obtaining information. After speaking to the required people, Mike will often then travel to a cave or other underground area. It is here that the game switches mechanics. The view is much more zoomed-in, with Mike traveling through rooms that are (usually) one screen big.

Mike initially attacks enemies with the Island yo-yo, renamed to the Island Star in the Virtual Console release, which has a short range. Later in the game, it can be upgraded to two more weapons adding range and power to his attacks, in order of appearance: the Shooting Star (Chapter 3 from SheCola) and the Supernova (Chapter 7 from the Orange Cube). These upgrades, however, require Mike's health to be at a certain level to be available, otherwise the item will change back to the next lower item. To use the Shooting Star, Mike needs 6 hearts full of life, and to use the Supernova Mike needs half of his health meter (11 hearts) full.

Mike can accumulate other weapons and magical items, some of which are baseball-themed, while some others were renamed according to the Operations Guide, in these areas, such as baseball bats, baseballs (also called wonder horsehides), cleats (also known as spikes), torches (titled as "fire"), bolas (also known as twisters), asterisk/twin cross-blades (which are similar to shurikens, but can split apart to move in a 90 degree angle), slingshots, reflective mirrors (known as "miracle mirrors"), two types of laser guns (a pistol and a rifle) and more. These special weapons do not carry over from dungeon to dungeon. In addition, Mike can collect several items that have different uses, such as a lantern for lighting darkened rooms, a snowman doll that freezes the enemy (used in chapter 2), the Rod of Sight used to make ghosts appear, the magic stopwatch that either slows or stops enemies, and a magic anklet that allows Mike to jump twice the distance until he moves to the next room.

Mike has a life meter which is made of a maximum of 22 hearts, similar to that of Link's. This meter can be expanded by finding Big Hearts (which are essentially the same as Heart Containers in Zelda). Sometimes a healing item called "Vitamin X" can be seen in some places in the game, which they can temporarily fill up all of Mike's hearts, while Mike's health will slowly drain to the amount of hearts he has. Mike loses hearts when he takes damage. These hearts can be refilled by finding hearts or stars either from enemies, or inside rooms, or by collecting 5 stars from enemies. Additionally, Mike can use stored potion to refill hearts when none are available. If Mike accidentally runs into a death trap, jumps into the water, or loses all his hearts, he turns into a ghost.

Mike has three lives and must restart from the beginning of a dungeon area if he loses them all. It is possible to have more than three lives, by obtaining the "Try-Your-Luck Signs" to either have more or less lives, depending on what number is shown on the sign. There are dozens of different enemies within the game and some instant-kill traps, such as spiked pits, platforms that sink into the ubiquitous water and giant bowling balls reminiscent of the rolling rock seen in the beginning of the Indiana Jones movie, Raiders of the Lost Ark.

Upon reaching the end of the dungeon area, Mike will usually fight a large boss character, which often requires a unique strategy to defeat. There is a point system in the game, which, unlike most games, reduces points for each enemy killed.

Immersive letter

A unique aspect of StarTropics was a saga involving a piece of paper, resembling parchment, that came packaged with the game. Written on it was a letter from Dr. Jones addressed to Mike, asking him to visit him at his laboratory on C-Island. It was as if the actual player had intercepted the message and was being invited indirectly to play the game. In later parts of the game, Mike receives an enigmatic message from his uncle through a third party:

"Evil aliens from a distant planet...." "Tell Mike to dip my letter in water...."

Even for a player who owned an original copy and thus, was more likely to have the letter, it was unusual for an NES game to refer to a physical object that would otherwise just be a novelty (although Infocom games had been doing this for some time, with the "Feelies" that they included with their games). This prompted the player to think that Dr. Jones might be referring to an object within the game. To add to the confusion of the puzzle, putting this paper under water might damage it. Regardless, the correct course of action was to dip the physical piece of paper in water. It revealed a secret message from Dr. Jones and the number "747" that must be used in the game in order to advance.

Since many rental stores and used video game retailers often do not have game boxes or manuals, it is difficult to find a copy of StarTropics with the original letter, requiring the use of game manuals or walkthroughs to complete this part of the game. Game magazine Nintendo Power was asked this question often enough that they published the "747" code as part of their "Counselor's Corner" soon after their article of the game. After completing the game a slideshow of events from the game is shown, including the letter being dipped in water and the number "747" visible on it.

For the Virtual Console release, the letter is included in the digital manual (Operations Guide) with an image of a letter and a bucket of water at the bottom. When the player clicks on one of the images, the letter dips into the bucket and the code is revealed. In the European release, the letter simply has a "click here" link at the bottom of the letter.