diff --git a/demos/gtk-demo/background.glsl b/demos/gtk-demo/background.glsl
index b807935a91..348cd16ae8 100644
--- a/demos/gtk-demo/background.glsl
+++ b/demos/gtk-demo/background.glsl
@@ -20,7 +20,7 @@ mainImage(out vec4 fragColor, in vec2 fragCoord, in vec2 resolution, in vec2 uv)
   float b = 1.0/distance (pos, p2);
   float sum = r + g + b;
 
-  float alpha = 1.0 - pow (1.0/(sum), 40)*pow (10.0, 40*0.7);
+  float alpha = 1.0 - pow (1.0/(sum), 40.0)*pow (10.0, 40.0*0.7);
 
   fragColor = vec4 (r*0.5, g*0.5, b*0.5, 1.0) * alpha;
 }
diff --git a/demos/gtk-demo/cogs.glsl b/demos/gtk-demo/cogs.glsl
index a0768bdb39..ee6ddb30c7 100644
--- a/demos/gtk-demo/cogs.glsl
+++ b/demos/gtk-demo/cogs.glsl
@@ -177,7 +177,7 @@ float ccell2(vec2 p, float r) {
 float df(vec2 p, float scale, inout vec2 nn) {
   p /= scale;
   nn = hextile(p);
-  nn = round(nn);
+  nn = floor(nn + 0.5);
   float r = hash(nn);
 
   float d;;
diff --git a/demos/gtk-demo/cogs2.glsl b/demos/gtk-demo/cogs2.glsl
index 8d131eca8d..518ae1ebdc 100644
--- a/demos/gtk-demo/cogs2.glsl
+++ b/demos/gtk-demo/cogs2.glsl
@@ -179,7 +179,7 @@ float ccell2(vec2 p, float r) {
 float df(vec2 p, float scale, inout vec2 nn) {
   p /= scale;
   nn = hextile(p);
-  nn = round(nn);
+  nn = floor(nn + 0.5);
   float r = hash(nn);
 
   float d;;
diff --git a/demos/gtk-demo/ripple.glsl b/demos/gtk-demo/ripple.glsl
index 028c14c159..a6e94d88c4 100644
--- a/demos/gtk-demo/ripple.glsl
+++ b/demos/gtk-demo/ripple.glsl
@@ -31,7 +31,7 @@ void mainImage(out vec4 fragColor, in vec2 fragCoord, in vec2 resolution, in vec
   float propagation_length = time * wave_speed;
 
   float t = (propagation_length - distance_from_center) / wave_length;
-  float offset_magnitude = 0;
+  float offset_magnitude = 0.0;
   if (t > 0.0)
     offset_magnitude = decay(wave_height * sin(t * 2.0 * PI), t);