Since you only have a limited supply of Inviso throughout the game (with small amounts resupplied to you every 10,000 points), it's important to use it sparingly. It is favorable to use Inviso over Hyperspace since you remain in control over the position of your ship. If you are about to be surround by enemies, thrust forward and use Inviso at the last second to escape collision, possibly taking an enemy out along the way. Once you are clear of any enemy, release Inviso as soon as possible. Then you can reverse and fire your lasers at the cluster of enemies you left behind.
The Stargate is an essential tool to any Humanoid defender. If no Humanoids are in trouble, the Stargate merely warps you to the opposite side of the planet. However, if you hear a Humanoid cry out for help, and you are no where near the abductee, dash to the Stargate as quickly as possible. You will be immediately warped to the location of the Lander trying to make off with the Humanoid. Prepare to fire at the Lander as soon as you arrive, but don't shoot the Humanoid! The Stargate can only take you to one endangered Humanoid, so be prepared to move on after you rescue the first Humanoid if any others are in trouble. If you rescue and capture four Humanoids, and fly through the Stargate without releasing any of them to the ground, you will immediately warp ahead three levels and earn 2000 point bonus for every humanoid that is left on that particular wave. This usually stops working after Round 10, but it can be adjusted by the arcade operator. Note: Reversing the ship just prior to entering the Stargate so it slides in backwards, from either direction, will override the warp, allowing you to continue rescuing humanoids.
Special round strategy
Every 5th round in Stargate is a special round. Each round ending with a 5 is an Yllabian Dogfight. Yllabian Dogfights contain nothing but Yllabian Space Guppies, Swarmers, and Dynamos. These can be extremely difficult, but extremely rewarding in terms of points. Stay cool and don't be tempted to blow through your entire supply of smart bombs or Inviso unless the enemies are relentless. Use the maneuverability of your ship to throw your enemies off. Every round that ends with a 0 is a Firebomber Showdown, which consists of Firebombers and Pods. Upon completion of the Yllabian dogfights a 2500 point bonus is awarded and on the Firebomber showdown waves a bonus of 500 points per surviving humanoid is awarded at the end of the wave. A full set of 10 Humanoids will be restored on the planet's surface after every 5 or 10 waves however this can be altered by the arcade operator.These special stages also mark the end of any apocalyptic mutant waves that you may encounter if every Humanoid in the world is destroyed.
Stargate can become very hectic, and it's important to prioritize your attacks to avoid the destruction of the world. Landers should be your highest priority above all the other enemies. Destroy any enemy that gets in your way, but if you have to decide between shooting a Lander or anything else, shoot the Lander since they represent the only direct threat to the Humanoids. When only three Humanoids are remaining on the surface of the planet, the world will begin to flash in order to warn you of the impending destruction. Select one or two Humanoids that you feel you can successfully guard and hover over them. A notice below the scanner will inform you when you have destroyed all of the Landers. That is you cue to destroy any remaining enemy. But don't take too long, or Baiters and the Munchy family of enemies will begin appearing.