There isn't a special technique. Fend 4 yurself
To enter Mordred's castle, solve the door puzzle. Click once on each of the 4 cards in the second row, the two middle cards in the 3rd row, and the 4 cards in the 4th row.
You have to click 10 of the cards exactly once each to flip them all over :all four cards in the 2nd rowthe two middle cards in the 3rd rowall four cards in the 4th row
To solve Mordred's puzzle and enter the castle, press each of the four cards in the second row (once), each of the four cards in the fourth row, and the middle cards in the third row.
To solve the puzzle, you have to press 10 of the panels exactly once each.They are :All four cards in the 2nd rowThe two middle cards of the 3rd rowAll four cards in the 4th row.
To open the door to the Binary bard's castle, you have to press 10 of the 20 "cards" exactly once each -- the cards are: All 4 cards in the second row. The middle 2 cards in the third row All 4 cards on the fourth row. The Bard is revealed to be ex-King Mordred.
The aliens are in the witch mountain building. You get them by finding all three colored key cards.
All you need to do is click all four of the cards once in the second row, then the two middle ones only in the 3rd row, and all four cards once in the 4th row. (see the related link)
The cards also flip adjacent cards. There is a simple process. Press each of these 10 cards exactly once, in any order: all four cards in row 2 the middle two cards in row 3 all four cards in row 4 (Reset first if necessary by refreshing your browser for Poptropica.)
you don't have to have cards, the cards are in the door. here is the code: first you press all the cards in the 2nd row, then press ONLY the two middle cards of the 3rd row, then press all the cards in the fourth row, so here is basically the numbers: 5, 6, 7, 8, 10, 11, 13, 14, 15, 16
For the Puzzle Door at the Bard's castle, you have to press 10 of the panels exactly once: Press all four cards in the 2nd row exactly once (in any order). Then press only the middle two cards of the 3rd row. Then press all four cards in the 4th row.
At the Binary Bard's secret planetoid, entering the castle requires you to flip over 20 "cards" or puzzle sections to reveal a hidden picture (and enter the castle). For the solution, see the related question.
There are many doors on Astro Knights island, but none appear to be blocked. The gate to the dungeon cell is opened with the switch when you enter through the library. The underground lab is opened with the small key (from under the village fountain). The dirt wall is easily knocked down to access the back of the dungeon cell. Later in the game, the Golden Key must be drawn and the cards must be turned to open the entrance to Mordred's castle. (see related questions)