replace noise with tileable perlin; use pixel-space sampling for fixed scale

shaders/vial_fill.gdshader

@@ -25,6 +25,7 @@ uniform float edge_pulse : hint_range(0.0, 2.0) = 1.0;
 // --- Distortion ---
 uniform sampler2D noise_tex : repeat_enable;
 uniform float noise_scale : hint_range(0.0, 5.0) = 1.0;
+uniform vec2 noise_module_size = vec2(300.0, 240.0);
 uniform float swirl_strength : hint_range(-2.0, 2.0) = 0.5;
 uniform float hue_shift_speed : hint_range(0.0, 5.0) = 0.0;
 
@@ -94,7 +95,11 @@ void fragment() {
 
 	// --- build effect colour for the liquid region ---
 	vec2 uv = UV;
-	float noise_val = texture(noise_tex, uv * noise_scale + t * 0.05).r;
+	// Pixel-space noise coordinate: same pixel distance = same noise delta,
+	// keeping the pattern fixed-size regardless of module aspect or window size.
+	// The 100.0 constant matches the noise texture size (100×100).
+	vec2 noise_uv = uv * noise_module_size / 100.0 * noise_scale + t * 0.05;
+	float noise_val = texture(noise_tex, noise_uv).r;
 
 	// wave distortion
 	uv.y += sin(uv.x * 10.0 + t) * wave_strength * noise_val;