Exploding Circles
To answer Gleeok's question: The Mine enemy changes to an Exploding Mine enemy (which has a blank graphic) when it runs out of hit points or gets close enough to the player. The exploding mine counts down for about 30 tics and then dies. Each tic, the exploding mine draws a transparent circle with radius equal to 10 times it's remaining life or something like that. Then it draws a random circle somewhere in the radius.
Damage is handled by an invisible enemy created when the Exploding Mine is created. The enemy is either offscreen or on top of the Exploding Mine, i forget which. When the player gets too close, the enemy is moved on top of the player for that frame.
Where do I go next?
To answer concerns about being lost: Yes. Eventually, most doors will have computer terminals the Guardian can use to hack into the enemy's network and get tips on her next location. Without it, your first goal is to travel right and down, then left through a water location, defeat several bosses, and get the Impact Saber and a few upgrades for your sidearm.
Then climb to the far northeast corner of Aquarius and travel left, using the Saber, to get Lev. 1 Missile Launcher.
Then travel left, going directly South of the starting location to open the door there, and across the forest, going to the treetops to open the door there. Finally, go south along the far left border of Aquarius to find Scorpio. You can pick up three or four missile packs on the way.
Of course, the result of all of this is that you earn the Bombs in Scorpio, which the quest starts you with. So you could skip all this and straight to the southwest region of Aquarius, get the Armor upgrade, then go 3 screens south of the starting location and left, taking you to Aries. In Aries, the high-jump is in the far lower left corner.
Once you have the high-jump, you can get to your second flying level in the far upper left of Aries, and the third level, below a destructible floor about seven or eight screens right of the starting location in Cancer.
And... so on like that.
It's too hard!
The initial flying level requires you to be on your toes, but it's not really too hard once you get the hang of your abilities. Obviously you want to memorize the attack patterns so you can kill as many baddies as possible without taking hits in return. Collecting health on the fly is vital because you WILL get hit occasionally.
The biggest key to SHUMP levels in Zodiac is to use your Bomb attack wisely. Holding "L" will fire a massive beam that tears up enemies caught in it for as long as you hold the button. But it uses up your energy, so you only can stockpile about two second's worth of the bomb. That's enough to clear all the enemies nearby. You can use it as your panic button when things get hairy, but the better use is to fire it up whenever you can nail five or more enemies at once. Your odds of one of them dropping an energy upgrade are pretty good, and once you refill your energy, you can fire the Bomb again.
The first boss should be easy once you get how to defeat it. The boss fires spreads of bullets that you can dodge by nudging through. But the four yellow crystals on it's wings fire more powerful seeker bullets, and occasionally fire cigar-shaped heat seekers that will track you until you destroy them. Enter the boss battle with full energy and focus your Bomb attack and shots on one side of the wing or the other until you destroy the yellow crystals. Then do the same on the other side, though you might be out of energy by then. Once you get rid of the crystals, the boss is a piece of cake - just nudge carefully through his bullet patterns.
And yea, you shouldn't be surprised that the enemies crush you if you skip ahead a few dozen levels without getting all the intervening upgrades!