Thexder was created by Hibiki Godai and Satoshi Uesaka, two programmers for Japanese developer Game Arts, and released in 1985. The game was massively popular and famously went on to sell over 500,000 copies in Japan. Because of this success, publisher/developer Sierra On-Line licensed the property for release in the United States. Sierra's ported version was released in 1987, and also became a best-seller. The game sold over one million copies worldwide, becoming one of the best-selling computer games up until that time. Thexder was an important breakthrough title for the run-and-gun shooter genre, paving the way for titles such as Contra and Metal Slug.
The Thexder Assault Vehicle is a "hyper dual-armor robot-jet transformer" (which basically means it can transform between robot and fighter jet modes). Equipped with heat-seeking lasers, a special shield system, and touch controlled flight mechanisms, Thexder is the ultimate fighting machine. There is only one Thexder in existence, and the protagonist is at its control.
As the game opens, Thexder becomes locked in a mysterious facility with no means of escape. The mission is to survive all 16 levels and disable the central computer, which creates the evil creatures that dwell in this forbidden world.
Each level is a massive side-scrolling map filled with obstacles, enemies, and various maze-like twists and turns. Play always begins on the far left side of the map and ends on the far right. The goal is simple: get from the beginning to the end whilst still having energy.
The Thexder Assault Vehicle can transform between two modes at any time: robot and jet. In robot mode, it can fire heat-seeking lasers to destroy enemies and obstacles. Although it has the ability to jump, Thexder's robot form is generally less mobile than its jet counterpart and therefore can't access certain areas of the level. In fighter jet mode, lasers can only be fired in a straight line, making the vehicle much less useful in combat. However, the jet's increased mobility allows it to reach areas that are higher and/or smaller than the robot's larger size would otherwise allow. To be successful, players need to master the balance between these two vehicle modes.
In addition to its offensive capabilities, Thexder is also equipped with an energy shield. At any time, players can choose to engage the shield by sacrificing a percentage of their current energy level. The shield provides invulnerability, but decreases with time and with each hit taken from an enemy. Completing a level without using the shield awards a sizable bonus to the "ENMAX" (the total possible energy points that are available to Thexder). Since later levels become much more difficult, it is important to have as much ENMAX as possible. Because of this, strategic use of the shield is essential for success.
Thexder is comprised of 16 levels, which become increasingly complex and/or difficult as the game goes on. The first four levels take place within some sort of ship or cargo hold, and are generally not too difficult. The next three levels (5-7) shift location to a series of underground caverns, where the enemies begin to become more difficult. Levels 8 through 12 mark a return to the earlier area, only this time the maps are significantly more maze-like and feature even tougher enemies. The final stretch features a quick return to the caverns (levels 13-15) which culminates in a confrontation with the central computer in level 16.
Each level contains a number of enemies and secret areas. Enemies can do serious damage to the vehicle and should typically be avoided or destroyed. However, there are a number of special creature types which, when destroyed, award increases to Thexder's ENMAX level. These special creatures are typically hidden away in secret areas, which can be uncovered with creative use of the laser. Finding as many of these ENMAX-increasing creatures as possible is critical.
- There is no traditional "ending" to the game. Completing all 16 levels just resets the game at level 1.
- The title screen music is Beethoven's "Moonlight Sonata".
- The Tandy version of Thexder is arguably the best, as it features 16-color 320x200 resolution graphics and full 3-channel sound.
- The TRS-80 Color Computer version of the game only contains five levels. The size was reduced to fit onto a 32 kB ROM cartridge (instead of a 720 kB floppy disk).