This makes a link. Whoever opens it reads your letter by dragging a finger across it, and every word burns as they pass. There is no second read.
The key stayed on this device and was never sent anywhere. The server is holding something it cannot read.
Anyone who opens this can read the letter — once. Send it the same way you'd send a key.
Tells you when the letter has been opened. Don't send it to them.
Letters are read by dragging a finger across them, so they only work on a touchscreen. Nothing has been opened yet — this link is still good.
Start at the circle. Drag right along each line, then drop down to the next.
Words appear just above your fingertip and burn out behind you. Keep going — if you stop for long, the rest goes too.
Nothing was kept. There is nothing to go back to.