mission 1, level 1: the main problem is getting used to the controls,as this is one of those games where up and jump use two buttons for any weird reasons. Tip: if you run out of ammo no worry,you have Infinite Ammo Basic Gun too.
level 2: this level is hardcore a bit. First problem is, the screen move old school, aka. when you reach the edge, not dinamic. Second: there are enemies shooting atyou bouncing projectiles, and it inclued some random factor, so they are VERY annoying. Some stuff also blocks your shots, just to make your life harder.
The key is to get to the top of the first tree, as somewhere there is a Temporal Invincibility item.
I also should look up some manual as those landmines are totaly useless, it'd be useful to switch to the grandes.
Tip: behind a tree jumping from the ground is a dose of super ammo. It can help, but as there's only 20, so it's very limited.
Note: there are some enemies jumping around meele,so keep your eyes open.
level 3: there are a crapton of items to collect, so you'll need a couple of goes. The colour code I have no idea where is, but the solution is 35241. I'm not sure about the Jumping Rockets, I feel you should be able to run close then duck to avoid them... But grenades or super ammo can destroy them too. The super ammo is better, as there was a rocket at the end I could not eliminate by grenades. Those green slugs also are not effected by Infinite Ammo, only super ammo and grenades.
level 4: the explosives are very limited, so pay attention if you go for max. score.
level 5: this is an enjoyably heavy level. There's also a secret level thingy above the rotating spiked rod. I found out the colour-coding solution: there'sa tiny box with the colour - only problem they are not distinct enough for me in such small size. Also: the maximum amount of lives is 9, so if you loose a couple, don't worry. Especialy as there's only level-saves.
The secret level had a megaton of extra lives.
6th has some falling platforms leading to some alternate route, but I could not manage that. Pro Tip though: although you die in water,m there are temporary platforms in the water under the skulls. Easier start thatway.
7th: it's a gauntlet, meaning there are respawning enemies and crap. Do NOT try to walk into blown up tanks, they case damage/instant death.
There are 2 bosses. For the skeleton aim for the head and try to dodge the hands. They hit you when they fall, but also just by flying aorund.
The final boss of this mission has a door you can teleport to a platform through and throw grenades, avoid its fire... Still not cakewalk, but very much ok. Thi introduces the next mission.
Unfortunately youcannot carry over levels your equipment,at least not in the GoG-version. Also you can not have more than 4 HP-bar. But the maximum lives seem to overflow, so that balances out. Also, as you can't carry over equipment, justsave and reload every level for a full heal
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Huah! Mission 2 is definitely harder. It starts with a tree-level what is annoying, although there are fewer platforms at least. When reached the ant level with wooden houses I got lost a lot, and for a looong time the start of the level is Infinite Pit With Temporary Platforms,aka. you have to reload if you fail anywhere, and it is easy to fail.
There's also boss, absolutely impossible to not loose a life or two, so get used to saving your progress. I wonder if I save ata waypoint that'd be saved or not. Should try.
There was a robot-boss. It's dumb. Just jump on the platforms, and when it is far jump lower and shoot. It helps that you can move the screen to see more with the pageup/down buttons.
On the level after that was a curiosity. Some beam transforms you to a slug. It CAN attack, despite how it feels. Try to mimic the AI-version's attack: jump in the air before striking for more effectiveness.
Then there's this "empty" level. Suspicious, eh? Don't leave after you put the crystal in its place but go back to the beginning. The secret level will make you loose a life, but will give back 4, so it's ok.
Need more life? Find a level which has "extra life" item, get it, save, reload, and you start with the extra life on you AND in the container again!
Note: seems the difference between difficult settings is the maximum HP-bar only. So as I play on Normal, 4 HP is correct.
The final level of Mission 2 is excelent. Isn't insenly hard, but makes you use all kinds of proper tactics, like duck&cover, move-the-screen-just-a-bit, hit&run, and even a well-places invincibility potion. Tip: the tanks at the start take 2 grenade (and sometimes a bit of ammo).
The final enemy is a bit tough, but there's a moveable block which gives you a safe place if you don't know where the boss is (because like falling down). The boss is not effected by the "target out of range" feature, so will follow you wherewere you are on the level, which is kinda amusing feat.