XF5700 Mantis Experimental Fighter

In what is possibly a rewrite of Williams's game, the invasion by the Sirian aliens (now dubbed "Sirians") takes place on March 16, 2094[2], leaving 3 billion humans dead. Earth was unprepared for the attack due to a recent war in the Middle East (Eurisian War) that took place thus exhasting the resources for defense against aliens. After Earth was devastated, the governments were dissolved in favor of a unified power called the Fist Of Earth. FOE is Earth's final hope to eliminate the Sirian threat. FOE's defenses is SolBase and the XF5700 Mantis. "Viper" (the player) is a Mantis pilot who was enlisted by FOE to fight the Sirians.

The aliens, which are now called "Sirians", are bug-like creatures which look like giant cockroaches, but have a strong collective group mind using telepathic messages when in groups. At first the Sirians were tiny "roaches" on their home planet, but as time passed, they evolved and eventually took over the dominant race on the planet Siria, wiped them out, and assimilated their technology. Siria later became uninhabitable. Sirians need vertebrate creatures in which to lay eggs to produces new Sirians; this is why the Sirians targeted Earth after searching for a new home planet.

Mantis had an advertising blurb which said "If you liked that other space sim, you will like Mantis!". The statement summed up the gameplay as playing Mantis is very hard to get used to. Using what was dubbed "real physics", the XF5700 Mantis could be flown in space as if it were real space physics, otherwise known as Newtonian physics. If you hit thrust, your craft would glide through space (like a boat through water). It will not change directions readily like in other space sims. 90 missions were loaded into the game. The AI was faulty at times, Sirian craft would always target the player and plot a suicide course against the player rather than trying to kill his/her wingmates. Some missions tended to be repetitive.