There are several ways to create a "one-way door", a passageway that enables travel in only one direction.
Dig out an underground passageway resembling the following picture. All the black blocks should be dug out; all the others should be solid. The colors are not important (they are used in the description below):
This passage can be traversed from left to right, but not from right to left. There are two ways to go from the left side to the right.
The first method is to stand on the yellow block, facing towards the green block. Now try to move towards the green block while hitting the jump button quickly and repeatedly. You will eventually end up in one of two places:
- You may end up with your feet inside the blue block. In this case you can simply move further forward, and you'll be on the lower passageway on the right.
- You may end up standing on the blue block with your head inside the green block (you'll see something like the Transparency Cheat). If this happens, press the jump button again. The result will depend on what type of device you have (iPad 1, iPhone 4S, etc.). You will either end up top of the green block, or below it (with your feet inside the blue block). In either case you can now move forward.
The other method is to increase your walking speed by placing an Energy Orb in your suit chest position (which normally has a Battery), as described in the Energy Orb article. Then start on the red block (or further back) and simply walk towards the green as fast as you can. The game will put you on the blue block with your head inside the green block. Then press the jump button and proceed forward.
As described above, the results of the first method (hitting the jump button many times fast) can be somewhat unpredictable. Also, where you end up depends on what type of device you have (new or old, iPad or iPhone, etc.). You may find one of these alternate versions to be more useful.
If you find that you always end up on the blue block with your head inside the green, and if jumping places you on top of the green block, you don't have to dig the lower exit passage and your one-way passageway can look like this:
- One-way passageway, simple step-up version
If you find that you always end up on the blue block with your head inside the green, you can make your one-way passageway like this. This allows you to move forward without hitting the jump button again. If you use the Energy Orb, you can zip right through this passage without any delay and without pressing jump at all:
- One-way passageway, simple step-down version
If you always end up with your feet inside the blue block, you can make your one-way passageway like this:
- One-way passageway with lower 2-block-high exit
If you sometimes end up with your feet inside the blue block, but sometimes with your feet on the blue block, you should make your one-way passageway like this:
- One-way passageway with 3-block-high exit
Depending on your device, some of the above passageways might work, and others might not. In some cases it even depends on how fast the game is running or the complexity of nearby terrain. Also, you might find that you can also get back through the one-way door (going right to left in the pictures) by walking into the green block while jumping. You may or may not want this. Try each of the versions shown above and use the one that works best.