diff --git a/solar_tracking.ic10 b/solar_tracking.ic10
index 4c6dd8a..2c16ba7 100644
--- a/solar_tracking.ic10
+++ b/solar_tracking.ic10
@@ -7,7 +7,7 @@ l r0 sensor Horizontal
 sb Solar Horizontal r0
 
 l r1 sensor Vertical
-add r1 r1 90
+sub r1 r1 90
 
 sb Solar Vertical r1