diff --git a/css/all.css b/css/all.css
index bd71e88..8645546 100644
--- a/css/all.css
+++ b/css/all.css
@@ -1,2 +1,2 @@
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\ No newline at end of file
diff --git a/less/all.less b/less/all.less
index 35ebf56..57f0d8b 100644
--- a/less/all.less
+++ b/less/all.less
@@ -18,6 +18,7 @@
 body{
     font-size: 24px;
     line-height: 32px;
+    text-rendering: optimizeLegibility;
 }
 
 h1, h2, h3, h4{