I have perfected my magma trap design.
This design has the following desirable properties:
- Instantly seals and fills after slightly more than a floodgate toggle delay, minimizing escape opportunities and doing away with lengthy waits for magma to flow.
- Instantly drains clean when finished, allowing immediate retrieval of valuable armor or admittance of another group to trap.
- Conserves magma, never permitting it to evaporate.
- Does not require use of magma-safe mechanisms.
- Equipped with an automated trigger/safety logic system, allowing the trap to be actuated without having to pull several levers (opportunities for the lever puller to fall asleep, or for the player to pull levers in the wrong order and cause a magma flood).
Its only requirements are magma-safe pumps and grates/floor bars (have sand or iron/nickel), a substantial amount of mechanical power (and therefore wood), and enough water volume to operate the logic system.
This proof-of-concept is a 10x1 tile hallway, but two copies of the trap could be placed face-to-face to make a 2-wide hallway, and it can be extended to any length desired.
Using this design with reversed logic would serve as a good freezing/thawing control for an ice trap.
See related map, trap diagram, and forum thread.