Implement cyclic animation reset opcode

engine/Age.Engine/Model/GfxState.cs

@@ -1097,6 +1097,37 @@ public sealed class GfxState
         }
     }
 
+    /// <summary>Op 0x230: stop every cyclic object channel without changing its base/current state,
+    /// one-shot channels, or retained cyclic targets. Native clears flag bit 2 and the five start/period
+    /// pairs at obj+0x20c..0x230, including one secondary matrix channel not otherwise modeled here.</summary>
+    public void ResetCyclicAnimationChannels(long handle)
+    {
+        lock (_lock)
+        {
+            var o = GetOrCreate(handle);
+            o.ColorStart = -1;
+            o.ScaleCycleStartMs = -1;
+            o.RotationStartMs = -1;
+            o.SrcStart = -1;
+            o.ColorPeriod = 0;
+            o.ScaleCyclePeriodMs = 0;
+            o.RotationPeriodMs = 0;
+            o.SrcPeriod = 0;
+            o.ColorAnim = false;
+            o.ScaleCycleEnabled = false;
+            o.RotationEnabled = false;
+            o.SrcAnim = false;
+
+            // Preserve drop-in numbered-save compatibility for the unmodeled secondary cyclic matrix
+            // as well as the modeled channels. The ten native timing dwords form one contiguous range.
+            if (o.NativePersistenceRecord is { Length: >= 0x234 } raw)
+            {
+                raw[0] &= 0xfb;
+                System.Array.Clear(raw, 0x20c, 0x28);
+            }
+        }
+    }
+
     /// <summary>Op 0x238: set its separate global animation-service duration and reset marker.</summary>
     public void SetAnimClock(long durationTicks)
     {

engine/Age.Engine/Vm/VirtualMachine.cs

@@ -2556,6 +2556,9 @@ public sealed class VirtualMachine
                 return pc + 1;
             case "u004223C0":   // 0x239 spritesheet cell: (handle)(delay)(duration)(frame count)(columns)(cell)
                 Gfx.SetSrcRect(Read(a[0]), Read(a[3]), Read(a[4]), Read(a[5]), 0); return pc + 1;
+            case "reset-gfx-cyclic-animations": // 0x230: stop all five retained looping channels
+            case "u00421E70":
+                Gfx.ResetCyclicAnimationChannels(Read(a[0])); return pc + 1;
             case "u00421EA0":   // 0x231 looping spritesheet: (handle)(ms per frame)(frame count)(columns)
                 Gfx.SetSrcRect(Read(a[0]), Read(a[2]), Read(a[3]), 0, Read(a[1])); return pc + 1;
             case "u00421EF0":   // 0x232 cyclic packed ARGB; negative alpha/RGB preserve static obj color