Dynamic Slope Linedef Special

[Uni-000]

This has definitely been done before, but here's my Take on it.

Dynamic Slopes, mainly for Cave-Ins or Avalanches, putting it into the Plane Align Special, or at the very least a Different Linedef Function that Controls the Slope of the Plane.

Obviously, the Arguments would be like this "how much do you want to Slope this Floor/Ceiling" and "how long should it take in tics for the plane to reach it's designated slope".

[Apeirogon]

https://github.com/coelckers/gzdoom/pull/223#