Trying to ID an old colour game

[Hateshinai]

Hi everybody, I'm new here and I'm looking for some help
I recently got a friend of mine hooked on retro handhelds. He is currently getting separated from his wife and decided that the best way to cope is by collecting Gameboys, Nintendo Game & Watch games and similar old games. This got me thinking about the games I had as a kid and there is one game whose name I can't remember. I would love to find out more about it (and some pics) since it was quite unusual at the time. Maybe someone can help to identify it. This is what I remember:
1. It was one of the old handheld LCD ones, similar to Game & Watch but definitely not a Nintendo one.
2. I had it about 25 years ago.
3. You controlled a guy who was defending a castle from (I think) dragons. In some places he would shoot arrows, in others he would use his sword.
4. Occasionally a princess would appear in the tower (or possibly dungeon, not too sure now) and would give you bonus points.
5. The unique thing was that it was actually in colour. It had a really messy LCD screen which made no sense on direct viewing but to play the game you would look through a polarised (I guess) second screen/filter which was at a 45 degrees angle to the LCD. You could close this filter thing flush with the game when not in use.
6. The game itself was white or a very light beige colour.
Any ideas?

[Rik]

I wasn't sure until you mentioned the pop-up screen...

That has to be Sunwing's Castle's Adventure:

http://www.handheldmuseum.com/Sunwing/CastlesAdventure.htm

I just sold one a month or so ago too... Not incredibly rare though, someone here might have one forsale...

Naughty Squirrel also used this same design:
http://www.handheldmuseum.com/Sunwing/NaughtySquirrel.htm
But obviously a very different game.

[Hateshinai]

That's it! Thank you so much!