The Guardian Legend (known as Guardic Gaiden in Japan) was a hybrid Action Game and Shoot Em Up created by Compile for the Nintendo Entertainment System. Released around 1988, it's likely forgotten by all but the most hardcore of gamers, but this game did a great job of blending the two genres.The game is about a female robot, codenamed "the Guardian", who is commissioned with stopping an alien-infested planet called Naju from crashing into Earth and killing everyone. To do this, she must set off ten strategically-placed explosives within the corridors (by transforming into a spaceship and flying through them) and defeat the bosses within.
Or not. The pyramids close slowly enough that you can run out before the boss appears if you're quick!
Boss Rush: "Corridor 21", and "TGL mode", which puts you through only the flying stages.
Boss Warning Siren: The normal music for the area turns off and a low and slow "bwoom" sound plays to warn of an oncoming boss. In the exploratory areas, this is accompanied by green pyramids closing off passages to other areas; it's possible to escape before the boss arrives. In ship areas, you have no choice and must confront the boss.
Difficult but Awesome: According to the UWW of this game, Lord Kat apparently discovered the ripple weapon being incredibly useful against the later bosses once fully upgraded. It's all a matter of using it correctly.
Explosive Breeder: One of the enemies in the labyrinth areas is a blue spider that if left unkilled, turns orange, then red, then it splits into seven identical copies of itself. These individual copies can split even more, making things a little... complicated.
Giant Space Flea from Nowhere: It (a.k.a The Final Guardian), the Final Boss, who appears out of nowhere after the Boss Rush, just when you think you're home free. (In a bout of Fridge Logic, it shouldn't matter that much if you beat it or not, since it only appears after you've succeeded in your mission to blow up the planet.)
If You Can Read This: All of the messages left to you by the last (good alien) survivor of NAJU comes in the form of giant monitors on the floor.
Insurmountable Waist High Fence - Those indestructible pyramids blocking your passage, until you gain enough speed upgrades to outrun the miniboss room ones or slip through the tiny gaps between the regular ones.
Intangible Man: You can easily walk though vertical 1-thin walls (apparently depends on a couple of factors, like emulator being used, etc) with enough speed upgrades.
Item Farming: You often have to farm enemies to get health and energy item drops before going into a corridor or optional boss fight.
Hitbox Dissonance: The game is extremely lenient when it comes to what parts of your sprite take damage, and what parts of enemy sprites give damage (especially the bosses). The fact that the game is still Nintendo Hard in spite of this says something.
They are also usually the easiest way to take down many of the otherwise challenging bosses. Lightsabers are just better, it seems.
Last Chance Hit Point: You will not die when your shields drop to zero. The next hit will destroy you, though.
Level Grinding: Killing enemies over and over will increase you score and eventually award you with one extra point of health. This ceases to be benefitial when at one million points you start needing another million for one health point.
The Lost Woods: The forest labyrinth area as well as the forest corridors.
Mercy Invincibility: Minimal, providing less than a second of protection, and only against small enemy collisions. Large lasers or enemy attacks do so much damage - sustained contact drains your shield almost instantly.
More Dakka: The Guardian's default gun relies on this principle. The more chips she's carrying, the more bullets-per-second she can shoot. The enemies also get this trope - in some of the later corridors, you'll find yourself facing an inspiringly absurd number of bullets and missiles and flying enemies and EVERYTHING ELSE.