Improve Herisson theme

Herisson/style/main.css

+/* Section polices */
+
+/* latin-ext */
+@font-face {
+  font-family: 'Source Serif Pro';
+  font-style: normal;
+  font-weight: 400;
+  src: local('Source Serif Pro'), local('SourceSerifPro-Regular'), url(fonts/source-serif-pro-ext.woff2) format('woff2');
+  unicode-range: U+0100-024F, U+0259, U+1E00-1EFF, U+2020, U+20A0-20AB, U+20AD-20CF, U+2113, U+2C60-2C7F, U+A720-A7FF;
+}
+/* latin */
+@font-face {
+  font-family: 'Source Serif Pro';
+  font-style: normal;
+  font-weight: 400;
+  src: local('Source Serif Pro'), local('SourceSerifPro-Regular'), url(fonts/source-serif-pro.woff2) format('woff2');
+  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+2000-206F, U+2074, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
+}
+
+
 * {
     box-sizing: border-box;
 }
 }
 
 html {
-    color: #313131;
-    font-family: "Open Sans";
+    color: #2a2230;
+    font-family: 'Source Serif Pro', serif;
     font-size: 22px;
     line-height: 1.5rem;
 }
 }
 
 body {
-    background-color: #f5f5f5;
+    background-color: #f8f6ff;
 }
 
 a {
-    color: #404c9e;
-
-    transition: color .2s ease-in-out;
-}
-a:hover {
-    color: #7586f0;
-    text-decoration: none;
+    color: #a6253a;
 }
 
 h1, h2, h3 {
 }
 
 .app-page-header {
-    padding-top: .5rem;
-    padding-bottom: .5rem;
-    margin-bottom: 2rem;
+    padding-top: 1rem;
+    padding-bottom: 1rem;
+    margin-bottom: 4rem;
 
-    box-shadow: 0 0 1px #313131;
+    background: linear-gradient(45deg, #c02b43 52vw,
+                                       #2a2230 52vw,
+                                       #2a2230 calc(52vw + 2px),
+                                       transparent calc(52vw + 2px));
+    border-bottom: 4px solid #2a2230;
 }
 .app-page-header .container {
     display: flex;
 }
 
 .app-page-header h1 a {
-    color: #313131;
+    color: #f8f6ff;
     text-decoration: none;
 }
 .app-page-header .app-page-header-title {