This door is very fun and very easy to make. A hidden door just pops out of the wall.
Step 1: Wall
Make a 3 tall, 4 long, and 1 wide wall. Then, one block away from that, make a 3 tall tower and connect
the top block to the wall. (By the way, the ingredients you'll need is stone, sticky pistons, a fence gate,
redstone, and a redstone repeater)
Step 2: Pistons
Go behind the wall. There, you put a 2 tall tower on the thick part. Next, put a 2 tall tower of sticky pistons
facing the wall next to the tower you just placed. Finally, put four sticky pistons (2x2) facing the 2 tall tower
and the first pistons you placed.
Step 3: Places That Redstone Will Go On
Place 2 blocks out from above the hole in the wall. Then, place 3 other blocks to the left of it,
place 2 blocks coming out at you from under the last block and mine that last block.
Step 4: Redstone and Fence
First, place 2 blocks up on top of your wall, all the way across the top. Then, on that ledge above the door, place redstone on top of both blocks. On the blocks leading out from that redstone dust, on the first block place a full tick repeater. On the second block, place redstone. Also put redstone along the other two blocks. Put a gate under the last one. Also, place a le above the blocks that are above the door and another underneath it, just on the other side. Hope it's fun.