Volfied

Story (from wikipedia)

Taking place in another galaxy, a space pilot is returning to his home world of Volfied, only to discover that it is under attack by an unknown alien force. The few remaining Volfied inhabitants are in an underground location of the planet and signal the pilot to their aid. The pilot flies to Volfied using his ship's defensive weapons in order to eliminate the alien threat and save his people.

Gameplay(from wikipedia)

The overall gameplay is identical to that of Qix. However, the main enemy is no longer a collection of lines - instead it varies between levels, and is always accompanied by smaller enemies. When the player's spaceship succeeds in claiming a section of the level, the side where the main enemy is taken as "the outside". Any smaller enemies ending up on "the inside" are killed, resulting in point bonuses. In order to complete a level, the player must claim at least 80% of a level's area. Previously, the limits were 75% in Qix and 70% in Super Qix. Each level in Volfied has a unique background and enemies. As the player claims areas of the level the cleared area graphic is replaced with the graphic of the next level. Grey boxes also appear on the field — these give the player a random power-up when collected. Power-ups can grant the player speed or even weapons. There is a special completion bonus on certain levels, often attained by shooting the main enemy.

Save the game whenever you want and continue from where you left even if you are out of lives. This capability will provide you to finish the overall game!