is there a way to fix it?

AFAIK, it's deliberate. The mouse is inaccurate and the keyboard moves it at half-speed. The joystick is a joystick in a top-down shooter.

so i should have to buy a joystick to play at the best?...

Playing a top-down with the joystick has it's own problems; it's not the best interface.
More precisely, use whichever you're most comfortable with.

Can Gog not fix these mouse issues?

The mouse control is really bad. This makes the game hardly playable with mouse.
Can gog or the developer fix this?

I noticed slight lag but I figured that it was deliberate (never played the original version). With practice and some anticipation I am able to play the game fairly competently, however, so I certainly would not call it unplayable.

Its not deliberate, its because we have newer mice and they didn't update the code properly =P

if you want to play this properly i recommend getting the original copy and playing it with dosbox =( would be nice to see a fix though... considering i paid 6 bucks to play this without having to use dosbox rofl =D

The mouse lag is a bug with this version specifically, however I contacted DotEmu (makers of the game) and they released a patch (How's THAT for customer service!). I'll contact GOG today to see if they've gotten ahold of the new DotEmu patched version...

Oh wow... Really disappointed about this mouse lag :(((

I don't see any mouse lag, even contrary, mouse moves faster than with keyboard and no such things like half speed or right corner is blocked so it's something related to system config not the application. Such mouse "gravity" or delay when you shooting and change move direction is simulation standard in DOS Games since Tyrian 2000 and present in many retro-homages (Jamestown and such). Still, I don't see any of the bugs people speaking about that much, even mouse is not a problem and not at half speed.

Same here. There's a small lag when using mouse. It's not as smooth and responsive as Tyrian 2000.
How can we get that patch DotEmu released? Is there any link?

I'm having the same mouse-lag issue as well. Is there a way to get the GOG version patched to fix this?

I really hope we get that patch to fix the mouse lag. It's so damn hard to avoid getting hit, even in the first level.