update game_menu

addons/PageFlip/Assets/page_flip_final.gdshader

@@ -0,0 +1,49 @@
+shader_type canvas_item;
+
+uniform sampler2D front_texture : source_color, filter_linear_mipmap;
+uniform sampler2D back_texture : source_color, filter_linear_mipmap;
+
+uniform sampler2D spine_shadow_gradient : source_color, filter_linear, repeat_disable;
+uniform float shadow_intensity : hint_range(0.0, 1.0) = 0.0;
+uniform float max_shadow_spread : hint_range(0.0, 1.0) = 0.35;
+
+uniform bool debug_mode = false;
+uniform bool is_backward = false;
+
+void fragment() {
+	vec2 uv_dx = dFdx(UV);
+	vec2 uv_dy = dFdy(UV);
+	float face_dir = uv_dx.x * uv_dy.y - uv_dx.y * uv_dy.x;
+	bool is_front = face_dir > 0.0;
+
+	vec4 base_color;
+	
+	if (is_front) {
+		if (is_backward) {
+			// Let's try flipping Y just in case they meant upside down!
+			// And keep X normal, since UV goes 0 to 1.
+			base_color = texture(front_texture, UV); 
+		} else {
+			base_color = texture(front_texture, UV);
+		}
+	} else {
+		if (is_backward) {
+			base_color = texture(back_texture, vec2(1.0 - UV.x, UV.y));
+		} else {
+			base_color = texture(back_texture, vec2(1.0 - UV.x, UV.y));
+		}
+	}
+
+	float current_spread = max_shadow_spread * (shadow_intensity + 0.001);
+	float sample_x = UV.x / current_spread;
+	float shadow_alpha = texture(spine_shadow_gradient, vec2(sample_x, 0.0)).a;
+
+	if (sample_x > 1.0) {
+		shadow_alpha = 0.0;
+	}
+
+	shadow_alpha *= shadow_intensity;
+
+	vec3 final_rgb = mix(base_color.rgb, vec3(0.0, 0.0, 0.0), shadow_alpha);
+	COLOR = vec4(final_rgb, base_color.a);
+}