Yes GDL is quite addictive. Hotspots are really cool for adjusting parameter values graphically. For a 2D angle you could use a script like this:
!Hotspots to control an angle parameter angleParameter
!about a center xC, yC. The hotspot is positioned at radius R.
hotspot2 xC, yC, iHotspot + 1, angleParameter, 6
hotspot2 xC + R*cos(angleParameter), yC + R*sin(angleParameter),
iHotspot + 2, angleParameter, 5
hotspot2 xC + 1, yC, iHotspot + 3, angleParameter, 4
iHotspot = iHotspot + 3
You can also move a hotspot in 2 dimensions at once.
BTW hotspots are discussed in more detail in the GDL Handbook.