Sub-Terrania

Sub-Terrania is a 1994 multidirectional shooter developed by Danish studio Zyrinx and published by Sega for the Mega Drive/Genesis. The game takes place in the future, where a deep-space mining colony has been invaded by an unknown alien race. The player assumes the role of a lone pilot who must defeat the alien forces and rescue the trapped miners. During the course of the game, the player controls a rotatable craft with thrusters that is constantly subject to gravity and the craft's inertia. Using the ship's 'rotate-and-thrust' capabilities, the players must aim, shoot, dodge and carefully maneuver their way through the hazardous landscape while constantly taking gravity and refueling needs into account.

It was the first game developed by Zyrinx, a small studio formed by people who had been active in the demoscene during the late 1980s and early 1990s. Upon its release, Sub-Terrania gained a reputation as an 'overly difficult' game and suffered from poor sales. However, critical reception was positive with game journalists describing it as an evolution of gravity-based shoot 'em up games like Gravitar (1982) and Thrust (1986). Critics praised its originality, graphics and soundtrack, while noting that getting used to the game's control system and physics-based gameplay can take some time.

On an off-world asteroid, a red line wipes the sky as headquarters explodes. Hostile alien forces have invaded the vital subterranean mining colony. Workers are trapped in crevices and chasms, helpless against the clouds of radioactive dust swirling toward them. An experimental attack fighter is the only weapon powerful enough to repel the alien attack. A lone pilot has been charged with the task of defeating the aliens and rescuing the trapped miners.

The game takes place in a side view underground environment. At all times, gravity is pulling down on the player's ship, which can work to the player's advantage to conserve fuel. The controls are similar to other gravity-based shoot 'em up games, like Gravitar and Thrust. The ship is rotated with the directional pad and the B button applies thrust in the direction it is facing. A key difference compared to other games of this type is the addition of back thrusters, which allow the players to reverse thrust as they try to dodge enemy fire and maneuver their way through the game's hazardous landscapes.

In Sub-Terrania, each level is an enclosed map in which the player is free to wander in all directions. To beat each of the game's 9 levels, the players must complete various mission objectives, which are outlined before the level begins (with the exception of the last three levels). The bulk of the missions involve rescuing trapped miners, carrying and utilizing various types of special equipment, collecting sub modules (to allow your attack ship to go underwater), and defeating alien bosses. While the players are, for the most part, free to approach things however they want, a key part of the gameplay revolves around finding efficient routes for each level.

The ship is equipped with a force field and will explode if it sustains too much enemy damage. It also has a limited supply of fuel and must be constantly recharged by collecting fuel canisters which are strategically placed throughout the levels, requiring players to plan when and where to refuel. There are various other elements that make it easier for the player to be able to finish without running out of fuel. Mining rails are suspended throughout many levels allowing players to freely slide along them while shooting. Attaching the ship on the rails turns off fuel consumption and nullifies the effects of gravity which can make for easier targeting against bosses and barriers. Scattered across the game's levels the players can find missile canisters (which equip the ship with secondary weapons), shield upgrades (which replenish the ship's force field), extra lives and various types of special equipment. When the 'Mega' bar is fully-charged, the ship can also unleash a powerful multi-directional laser blast. Once used, the bar gets depleted and begins to recharge automatically.

There are three types of weapons in the game, identified by three different colors (red, green and blue). Each weapon type has its own upsides, downsides and different strategies, with varying degrees of destructive power, range and a different effect on the rate of the ship's fuel-consumption. All three weapon types can be upgraded up to level 4 by collecting power-ups which cycle though red, green and blue. The player can either take on the color of the laser they already have to increase its firepower by one level, or they can take on a different color to change the laser's attributes. When players lose a life, their weapon's power is downgraded by one level. However, this does not apply on Easy mode, in which players are allowed to retain their weapon enhancements even after losing a life.

Sub-Terrania features three difficulty modes (Easy, Normal and Hard), all available from the start. Each difficulty mode affects the rate of fuel-consumption, the strength of the gravitational pull, the intensity of inertia, the amount of enemy damage that players can sustain and the amount of bonus points at the end of each stage. In Sub-Terrania, players earn points for shooting down enemies and are also rewarded with end-of-level bonus points based on their overall performance. This includes their remaining lives after a mission, the number of enemies destroyed, the number of POWs rescued and their time-efficiency in completing the mission. Compared to normal mode, players get half as many points on easy and twice as many on hard.