The flying thing on the castle top
On THE CASTLE TOP something flies back and forth over the gap between a pillar and a platform on the left, and hits Seymour whenever he jumps across.
Nudge 1Where to look
It always flies the same path at the same speed. It's a matter of timing.
Nudge 2A stronger push
Stand on the pillar and watch it. Jump when it has just passed you, going away.
Nudge 3Almost there
Starting the jump while it's in the middle of its path (not at either end) is safest.
What you needOther problems to solve first
Solve these first (each opens its own page, no answers on the way):
Show the solutionThe whole answer, with a video
Wait on the pillar until the flyer is roughly in the middle of its run and heading away, then jump left onto the platform and pick up the studio key (it opens the Sherlock Bones door in the maze). Coming back, time it the same way. A save (F5) before the jump costs nothing.
Why it works
Patrolling creatures move one pixel per step between two fixed ends and hurt Seymour while they overlap him; their position doesn't depend on Seymour at all.