Linedef type 254

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Knuckles destroying a bustable block.

Linedef type 254, Bustable Block, is a type of floor over floor block which will shatter when spindashed into from the side. This block cannot be broken from above or below. When shattered, it generates the bustable block sprites, produces crumbling ambience (sound sfx_crumbl), and hides inside the floor of the sector it is in. This allows it to be respawned after it is busted by raising it back up to its former height. Knuckles will break this block on contact due to his strength, as will any custom character who has the Glide/Climb ability (CA_GLIDEANDCLIMB). When it is set to have a texture similar to that of surrounding sectors, it is useful for concealing secret items or paths in a level.


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 controlling 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.

If the Not Climbable flag is checked, this block can only be busted by Knuckles, or by a custom character whose ability S_SKIN value is set to CA_GLIDEANDCLIMB. This is useful for creating Knuckles-only paths in a level. If the Solid Midtexture flag is checked, this block can be shattered by a pushable Object. If the Repeat Midtexture flag is checked, a linedef executor will be activated when the block is shattered. In this situation, the tag of the trigger linedef of the linedef executor to activate is determined by the length of the controlling linedef.


Because bustable blocks turn off FF_EXISTS when shattered, effectively making them disappear completely, they must be respawned by turning on this flag again. The most convenient way of doing this is using the Make FOF Disappear/Reappear (linedef type 445) linedef executor with the Not Climbable flag applied, which will immediately make the FOF reappear when executed. The Make FOF Disappear/Reappear linedef should have its front X texture offsets match the tag of the FOF's target sector in-level, and front Y texture offsets matching the tag of the FOF's control sector.

To create a timed respawning effect, the FOF's control linedef should be given the Repeat Midtexture flag and given a length that corresponds with the tag of the trigger linedef (e.g., Continuous) to execute the Make FOF Disappear/Reappear linedef, as this then allows the FOF's destruction to execute the linedef. The Make FOF Disappear/Reappear linedef itself should then be given a delay using the Upper Unpegged flag – a back sector for the linedef is then needed to determine the delay in tics, which corresponds to the sector's ceiling height.

Alternatively, Lua is also capable of turning back on FF_EXISTS in the FOF's flags – this requires searching through all FOFs located in the FOF's target sector to find the one you want.

Example code using "sector" as a sector_t variable, and "rover" as a ffloor_t variable, and turning on FF_EXISTS for any FOF if it is not already applied:

for rover in sector.ffloors()
	if not (rover.flags & FF_EXISTS)
		rover.flags = $1 | FF_EXISTS


Sample 1

Example WAD: ex_ld254_fofbustableblock.wad

Sample 2

Example WAD: ex_ld254_fofbustableblock_knuckles.wad
  • This example WAD can be played in any gametype. It uses MAP01, replacing Greenflower Zone Act 1.
  • This bustable block can be only shattered by Knuckles or any skin with the ability 2.
  Linedef typesFloor over floor [view]
Solid, Opaque, ShadowcastingSolid, Opaque, Non-ShadowcastingSolid, TranslucentSolid, Sides OnlySolid, No SidesSolid, InvisibleIntangible from Bottom, OpaqueIntangible from Bottom, TranslucentIntangible from Bottom, Translucent, No SidesIntangible from Top, OpaqueIntangible from Top, TranslucentIntangible from Top, Translucent, No SidesOnly Tangible from Sides
Water, OpaqueWater, TranslucentWater, Opaque, No SidesWater, Translucent, No SidesGoo Water, TranslucentGoo Water, Translucent, No SidesIntangible, OpaqueIntangible, TranslucentIntangible, Sides OnlyIntangible, Invisible
Air BobbingAir Bobbing (Adjustable)Reverse Air Bobbing (Adjustable)Floating, BobbingRising Platform, Solid, Opaque, ShadowcastingRising Platform, Solid, Opaque, Non-ShadowcastingRising Platform, Solid, TranslucentRising Platform, Solid, InvisibleRising Platform, Intangible from Bottom, OpaqueRising Platform, Intangible from Bottom, Translucent
Crumbling, RespawnCrumbling, No RespawnCrumbling, Respawn, Intangible from BottomCrumbling, No Respawn, Intangible from BottomCrumbling, Respawn, Intangible from Bottom, TranslucentCrumbling, No Respawn, Intangible from Bottom, TranslucentCrumbling, Respawn, Floating, BobbingCrumbling, No Respawn, Floating, BobbingCrumbling, Respawn, FloatingCrumbling, No Respawn, FloatingCrumbling, Respawn, Air Bobbing
Light BlockHalf Light BlockFog BlockMario BlockThwomp BlockShatter BlockShatter Block, TranslucentBustable BlockSpin-Bustable BlockSpin-Bustable Block, TranslucentQuicksandLaserCustom FOF