A game originally published by Sierra Online for the Apple //GS and later ported to IBM.

In Thexder, the player controlled a vehicle similar to the Veritech Fighter from Robotech, although there was no guardian mode. In battloid mode, the vehicle was optimized for combat. It could run and jump to a limitted height, and control its lateral movement while in mid-jump. In addition, when fired the vehicle's laser would automatically attack any enemies within an arc in front of the vehicle approximately 130 degrees wide while in battloid mode. In fighter mode, optimized for freedom of movement, verticle movement was not restricted, however the vehicle's laser would only fire straight ahead.

The graphical presentation of Thexder was more or less like that of a traditional, side scrolling shooter with the addition of vertical scrolling as well. Each level took place in a maze. Often times, the maze would limit the player in that the vehicle could only traverse certain areas while in fighter mode, due to the fact that the fighter would fit into smaller passageways and would also scale large verticle obstacles that could not be jumped over while in fighter mode.

The vehicle had an energy reserve. The energy reserve could be depleted in one of three ways. First, the laser would use 2% of the vehicles "maximum" energy (the vehicle's energy could be increased above 100% by power ups) for every 30 shots fired. Second, coming into contact with an enemy vehicle or other obstacles such as lava pits would drain the energy very rapidly. Third, at the expense of a large amount of energy, the player could activate an energy shield that could absorb a large amount of damage but would dissipate on its own over time. When the energy level reached zero, the vehicle would explode and the game would end.

Given the //GS's rather limitted graphical capabilities, even by the standards of the day, Thexder succeeded in being both fun, challenging, and visually impressive. The best part was watching the vehicle transform between its two modes. The use of sound, one of the //GS's strong points (It could truly produce 15 simultaneous 8-bit digital voices when even years later most PC's had sound blaster cards with a single 8-bit digital voice) was first rate. The game even played a soothing rendition of Beethoven's Moonlight Sonata while idling.