Most of the Achievements are self-explanatory, and will be gained during the 10+ runs you'll need to do to get all the Kills knotched up. I'd recommend starting from Easy if you're just after the 100% as it allows you to get overpowered nice and early.

But there are 4 which are a bit tricky; this guide is just a quick tutorial on how to get those.

Description: "Make One Hero Obtain All Medals".

This one is tricky because weirdly, you can miss one of the medals if you're too enthusiastic. On my third run through on Hard, I noticed that I'd never scored below 70% Ground Targets destroyed, and you don't get the lower medals if you do.

This is complicated by the fact that anything that explodes near the ground, be it homing missiles or crashing destroyed enemies can destroy the targets too.

I'd recommend on a first Easy run taking NO BOMBS and using Mission 2: Crates, as there are plenty of scaffolds which cover the targets; fly as high as you can, shooting as little as possible, and run the mission until you get the 50% Medal. You should get 70% and 90% as you play further into the game, but keep an eye on this because it's easy to get carried away smashing everything to earn money. You need ALL medals, remember.

Description: "Finish Campaign without being shot down".

Sounds daunting at first, but this one is easy to cheese. Save the game at the start of every level, and if ever you lose your ship, instead of respawning, reload the level save which resets your shot down counter.

Description: "Kill 60 troops with one hit".

Somewhat obvious, but that blood lust gets in the way again and can be missed; Equip a Cauldron bomb, and on any level with Zombies (Level 9: Zoo in particular, especially the final boss), wait as long as possible with no firing until plenty are walking below you, then drop said bomb.

Description: "Reach score of 10,000 in Tetrix"

Extremely frustrating, and all I can do is offer you basic suggestions here.

Firstly, DONT play it like classic Tetris. In particular, don't play fast; there are no points bonus for dropping pieces, but rather a slowly rising number of points per line. There also doesn't seem to be a bonus for multiple lines, so don't build high and try and fill with the 3 piece line; build flat and clear lines as soon as possible, you want as clean a field as you can keep.

Move very, very slowly. Take the time to work out precisely where to place the piece. You can fill in a few gaps with the single square too, so don't worry about missing one, as long as there's a path to the lowest point.

At Round 2, the + piece turns up. This is annoying but try and treat it like the T shape with an extra bit; you want a U shaped sort of gap for it to slot into, but where none exists, place the bottom part in a step, a _| or |_ , and try and fill the resulting gap to the left or right with a single. You want to still be near the bottom by the time you pass this round.

At Round 4 the S shape turns up. It's horrifying at first but try and think of these as an L shape with an extra bit. You want to prioritise placing it with the 3 squares horizontal. Unfortunately, from here on it's down to luck whether you can make it, as if you get too many you're just going to be knackered.

You should beat the achievement by the time Round 5 starts, your aim is just to keep clearing single lines as best you can and hope you can crawl over the finish line.

Good luck. Sorry I can't be of more help here.