diff --git a/samples/bin/library/sdf_shader.frag b/samples/bin/library/sdf_shader.frag
index 9047aa37..c6958018 100644
--- a/samples/bin/library/sdf_shader.frag
+++ b/samples/bin/library/sdf_shader.frag
@@ -14,14 +14,14 @@ varying vec4 v_color;
 
 void main() {
     float distance = 1.0 - texture2D(u_texture, v_st0).a;
-    float alpha = smoothstep(u_char_width + u_char_edge, u_char_width, distance);
+    float alpha = 1.0 - smoothstep(u_char_width, u_char_width + u_char_edge, distance);
 
-    float outline_alpha = smoothstep(u_outline_width + u_outline_edge, u_outline_width, distance);
+    float outline_alpha = 1.0 - smoothstep(u_outline_width, u_outline_width + u_outline_edge, distance);
     float overall_alpha = alpha + (1.0 - alpha) * outline_alpha;
     vec4 overall_color = mix(u_outline_color, v_color, alpha / overall_alpha);
 
     float distance_shadow = 1.0 - texture2D(u_texture, v_st0 + u_shadow_offset).a;
-    float shadow_alpha = smoothstep(u_shadow_width + u_shadow_edge, u_shadow_width, distance_shadow);
+    float shadow_alpha = 1.0 - smoothstep(u_shadow_width, u_shadow_width + u_shadow_edge, distance_shadow);
     vec4  shadow = vec4(u_shadow_color.rgb, shadow_alpha);
 
     gl_FragColor = mix(shadow, overall_color, overall_alpha);