diff --git a/tools/transpile-engine/transpile.py b/tools/transpile-engine/transpile.py
index c3e45d01..3f7df487 100644
--- a/tools/transpile-engine/transpile.py
+++ b/tools/transpile-engine/transpile.py
@@ -61,6 +61,7 @@ REQUIRED_GD_FUNCTIONS: list[tuple[str, str]] = [
     ("climate",           "_update_lake_evaporation"),
     ("climate",           "_update_deep_earth_water"),
     ("climate",           "_update_precipitation"),
+    ("climate_base",      "_check_terrain_evolution"),
     ("climate",           "_compute_global_stats"),
     ("climate",           "_clear_magic_deltas"),
     ("climate_spec_eval", "ideal_terrain"),
@@ -182,6 +183,7 @@ METHOD_MAP = [
     ("_update_lake_evaporation",     "stepLakeEvaporation",    "private"),
     ("_update_deep_earth_water",     "stepDeepEarthWater",     "private"),
     ("_update_precipitation",        "stepPrecipitation",      "private"),
+    ("_check_terrain_evolution",     "stepTerrainEvolution",   "HAND_WRITTEN"),
     ("_compute_global_stats",        "stepGlobalStats",        "private"),
     ("_clear_magic_deltas",          "stepClearDeltas",        "private"),
 ]
@@ -353,6 +355,7 @@ export class ClimatePhysics {
     this.stepLakeEvaporation(grid)
     this.stepDeepEarthWater(grid)
     this.stepPrecipitation(grid)
+    this.stepTerrainEvolution(grid)
     const events = this.stepEcologicalEvents(grid, turn, seed)
     this.stepAnchorDecay(grid)
     this.stepGlobalStats(grid)
@@ -361,25 +364,24 @@ export class ClimatePhysics {
   }
 
   private stepOrbitalForcing(grid: GridState, turn: number): void {
-    const orbitalRaw = (this.params as Record<string, unknown>)['orbital_cycles']
-    if (!orbitalRaw) return
-    const orbital = orbitalRaw as Record<string, unknown>
-    const cycles = (orbital['cycles'] ?? []) as Array<Record<string, number>>
-    if (cycles.length === 0) return
-
-    let totalDelta = 0.0
     const t = turn
-    for (const cycle of cycles) {
-      const period = cycle['period'] ?? 200.0
-      const amplitude = cycle['amplitude'] ?? 0.01
-      const phase = cycle['phase'] ?? 0.0
+    let totalDelta = 0.0
+    for (let i = 1; i <= 3; i++) {
+      const prefix = `orbital_cycle_${i}_`
+      const period = this.p(prefix + 'period', 0.0)
+      if (period <= 0.0) continue
+      const amplitude = this.p(prefix + 'amplitude', 0.0)
+      const phase = this.p(prefix + 'phase', 0.0)
       totalDelta += amplitude * Math.sin(2 * Math.PI * (t / period) + phase)
     }
 
     if (Math.abs(totalDelta) < 0.0001) return
 
+    const moistureCoupling = this.p('orbital_moisture_coupling', 0.5)
+
     for (const tile of grid.tiles) {
       tile.magic_heat_delta += totalDelta
+      tile.magic_moisture_delta += totalDelta * moistureCoupling
     }
   }