Post Game jam commit

shaders/fade_in.gdshader

@@ -0,0 +1,13 @@
+shader_type canvas_item;
+uniform sampler2D mask; // a texture
+uniform float progress : hint_range(0.0, 1.0, 0.001);
+
+void fragment() {
+    float mask_value = texture(mask, UV).r;
+
+    // ensure the progress is a bit bigger than the feather
+    float threshold = progress * 1.001;
+
+    // Fade alpha based on mask vs. threshold with a feather
+    COLOR.a *= smoothstep(threshold, threshold * 0.999, mask_value);
+}