diff --git a/app/src/main/res/raw/tiltshift_fragment.glsl b/app/src/main/res/raw/tiltshift_fragment.glsl
index 72a6a30..e05ee2c 100644
--- a/app/src/main/res/raw/tiltshift_fragment.glsl
+++ b/app/src/main/res/raw/tiltshift_fragment.glsl
@@ -24,11 +24,14 @@ varying vec2 vTexCoord;
 // Calculate signed distance from the focus region for LINEAR mode
 float linearFocusDistance(vec2 uv) {
     // Center point of the focus region
-    vec2 center = vec2(uPositionX, uPositionY);
+    // Transform from screen coordinates to texture coordinates (90° rotation)
+    // Screen (x,y) -> Texture (y, 1-x)
+    vec2 center = vec2(uPositionY, 1.0 - uPositionX);
     vec2 offset = uv - center;
 
-    // Adjust angle by -90 degrees to compensate for portrait texture rotation
-    float adjustedAngle = uAngle - 1.5707963;
+    // Adjust angle by +90 degrees to compensate for the coordinate transformation
+    // The position transform is a 90° CW rotation, so angles transform as θ + 90°
+    float adjustedAngle = uAngle + 1.5707963;
     float cosA = cos(adjustedAngle);
     float sinA = sin(adjustedAngle);
 
@@ -41,7 +44,9 @@ float linearFocusDistance(vec2 uv) {
 // Calculate signed distance from the focus region for RADIAL mode
 float radialFocusDistance(vec2 uv) {
     // Center point of the focus region
-    vec2 center = vec2(uPositionX, uPositionY);
+    // Transform from screen coordinates to texture coordinates (90° rotation)
+    // Screen (x,y) -> Texture (y, 1-x)
+    vec2 center = vec2(uPositionY, 1.0 - uPositionX);
     vec2 offset = uv - center;
 
     // Adjust for aspect ratio to create ellipse
@@ -50,7 +55,8 @@ float radialFocusDistance(vec2 uv) {
     offset.x *= screenAspect;
 
     // Apply rotation
-    float adjustedAngle = uAngle - 1.5707963;
+    // Adjust angle by +90 degrees to compensate for the coordinate transformation
+    float adjustedAngle = uAngle + 1.5707963;
     float cosA = cos(adjustedAngle);
     float sinA = sin(adjustedAngle);
     vec2 rotated = vec2(
@@ -107,7 +113,8 @@ vec4 sampleBlurred(vec2 uv, float blur) {
     vec2 blurDir;
     if (uMode == 1) {
         // Radial: blur away from center
-        vec2 center = vec2(uPositionX, uPositionY);
+        // Transform from screen coordinates to texture coordinates (90° rotation)
+        vec2 center = vec2(uPositionY, 1.0 - uPositionX);
         vec2 toCenter = uv - center;
         float len = length(toCenter);
         if (len > 0.001) {
@@ -117,7 +124,8 @@ vec4 sampleBlurred(vec2 uv, float blur) {
         }
     } else {
         // Linear: blur perpendicular to focus line
-        float blurAngle = uAngle;
+        // Adjust angle for coordinate transformation
+        float blurAngle = uAngle + 1.5707963;
         blurDir = vec2(cos(blurAngle), sin(blurAngle));
     }