Use arrow keys to move. The horseshoe thing is a magnet, it attracts anything metal in the same room, keys/sword. No, no other controls. The duck things are dragons, there are three, red is fastest.
Kill the dragons with the sword.
There were 3 levels in original game, level 2 had 2 castles etc. Then it repeated with the dragons moving faster for levels 4,5,6.
The goal of the game is to get the Chalice (flashy thing) back to your yellow castle. Keys open corresponding doors.
Pretty simple really..