Brainsnag Level 9 answer: Wake the Guard
The level says: “Get through the gate”
Hints first (no spoilers)
Hint 1Sneaking will not work. Maybe waking him up is the point.
Hint 2Alarm clocks ring when they get a good shake.
Hint 3Shake your phone (or wiggle the phone graphic back and forth fast). The alarm rings, the guard wakes and opens the gate.
Show the full solution
Dragging the key to the lock fails because the guard hears it. Instead, shake the device so the alarm clock rings. On desktop, drag the phone graphic rapidly side to side. The guard wakes up and opens the gate for you.