I had scribbled out the basics of an encounter and thought I'd share now that the current round is done. I don't believe we can upload art to the forums easily, so you will have to use your imaginations from the description below.
Starting with my usual duff name, of which I hadn't yet decided which to use ( you know, the meme, what were you thinking one would probably have been picked as I was weaned on the old Letter-Number Modules or yore... )
"The Clock Strikes Death", "Time Runs Over", "Chime Time"
The premise was that the encounter would take place inside a huge town centre water driven clock. The combat would be in the main clock mechanism.
On entry to the room, the party finds a sound wall blocking egress to the main mechanism chamber, set in the centre of which is an enormous spring that when operative provides a round by round entry way as the spring contracts.
It can be seen that the end of the spring is connected to a water wheel driven by a subterranean stream, so "powering" the clock indefinitely.
Wedged in the spring preventing it from coiling and uncoiling is the body of the clock attendant. Foul Play indeed.
Once the party removes the body, the spring starts to tick and the sound of turning gears and furtive movements can be heard from the main works area. The turning water wheel effectively gets the spring to pulse on a round by round basis, which when at its tightest point allows a single PC per round to pass into the main encounter room. There would likely have been some bludgeoning damage from the spring for PC's trying to rush through, but the encounter design wasn't completed - I leave this to my fellow inventive GM's.
The main encounter room behind the spring retaining sound wall has a number of features on two levels.
At the east and west side of the rooms are chain belts that would be used as escalators/ladders to the above floor east and west maintenance gantries (which is where the ranged opponents would be situated to rain arrows and death down upon the party).
The lower and upper floors would consist of 3 sizes of interlocking gears, standing on the gears, you would rotate at different speeds per round such that melee encounters with the non gantry ground forces would be extremely mobile requiring constant positional movement and would certainly challenge flanking skills.
The upper area has gears that drive an outer hollow rod that raises through the ceiling, driving the hour hand of the clock face outside.
The lower gears, being faster drive a central smaller rod that rises up inside the larger one above and drives the minute hand.
The gears lie in the main horizontally, forming the floor of the two levels, so by standing on the different gears is how the environment moves combatants around on a per round basis. (remember, removal of the dead body to gain access to this room effectively restarts the clock mechanism).
Hanging from the ceiling between the east and west gantries are the bell chimes, the clappers of each bell sufficiently spaced to allow the acrobatic PC the opportunity to swing across from one upper gantry to the other gantry.
Gaining access to the second floor level is achieved by riding a vertical gear that interlocks between both levels or by jumping from the gantries, or by riding the water wheel and jumping at the top of that.
I would probably have had some sort of balance type of check under given conditions and some environmental "falling into the gears" type of damage and maybe a time limit before the room occupants face a sonic barrage as the bells are rung at something o'clock, but didn't get that far in the design.
There you go, that was the basic guts of what I was thinking had I made successful entry to the competition.
I hope you like the idea and maybe can make use of it.
Enjoy.