First you must kill that gamepad robot at the beginning. If it flees you are in a deep trouble, as it can easily wear you down with its missiles an vulcan.
Then you must rush past the enemies to get the cloaking device. Then get the blue key and clear the yellow key room. You must do this because there isn't enough room to fight with the diamond claws with laser (their green blobs are hard to dodge on the close range). If you get the cloaking device and you fight in the big room then eventually you need to destroy at least 3 sidearms and their modules are very problematic to kill and they make you blind easily. So you must get past them and into the yellow key room. A grid will shout behind you.
The yellow key hollow trigger opening two secret doors. Several diamond claw will attack you. But make sure you don't break the switch behind the afterburner, so you can make a dead end that will be your base for now to attack out from.
Now you can exit from that narrow corridor, that's generally easy to clear. But behind the waterwall a sidearm awaits you, use the smart missile to destroy it (note that large mechs tend to self-destruct if they got stuck, that's happened)
Then the final hard part is getting the gauss from this point, a gamepad robot is there that can deal a great amount damage if you are careless...
If you managed to get this far and have the gauss cannion. The rest of the level shouldn't be a problem.
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