Thing type 523, Spike, is a type of Thing that is a spike attached to the floor. The spike itself is intangible by default and does not hurt players when they touch its tip. For the spike to hurt players, you must either check the Ambush flag or put an invisible, intangible FOF with spike damage over the area where the spike is placed.
If the Special flag is checked, the spike will periodically retract into the ground and pop up again, playing a sound every time it does so. The default interval at which the spike pops up/retracts is set by the Object's Speed value, which is 2*TICRATE (2 seconds). Additionally, the interval can be modified with the Thing's Angle value. The Angle value, in tics, is added to the interval. 35 tics equal one second, so for example an Angle value of 70 will add two seconds to the interval, extending it to four seconds. Negative values can also be used to shorten the interval.
