Linedef type 153, Dynamically Sinking Platform, is a type of floor over floor platform which will sink when stood upon by a player. The FOF will slowly return to its original height when the player is no longer standing upon it, but it rises much slower than it sinks, so the player cannot keep it at an even height by jumping in place. This FOF type is used in Red Volcano Zone Act 1 to create platforms that sink into the lava.
Setup
The flats, floor height, and ceiling height of the FOF are determined by the flats, floor height, and ceiling height of the control sector, and the sidedefs of the FOF's walls are determined by the sidedef of the control linedef.
The light level of the control sector will determine the brightness of the shadow cast by the FOF. If the light level of the control sector is lower than that of the target sector, then it will cast a dark shadow. If the light level of the control sector is higher than that of the target sector, then the FOF will illuminate the area below it. If the light level of the control sector is equal to that of the target sector, then the FOF will not affect the light of the area below it.
The sinking distance is determined by the length of the control linedef. If Flag [6] / Not Climbable is used, the player will be required to spindash to make the FOF move.