ADDED   gc_lang/fr/webext/content_scripts/content_panels.css
Index: gc_lang/fr/webext/content_scripts/content_panels.css
==================================================================
--- gc_lang/fr/webext/content_scripts/content_panels.css
+++ gc_lang/fr/webext/content_scripts/content_panels.css
@@ -0,0 +1,71 @@
+/*
+    CSS
+    Content panels for Grammalecte
+*/
+
+.grammalecte_panel {
+    padding: 0;
+    margin: 0;
+    position: fixed;
+    left: 50%;
+    top: 50%;
+    z-index: 100;
+    border: 10px solid hsla(210, 20%, 70%, .5);
+    border-radius: 10px;
+    background-color: hsl(210, 20%, 90%);
+    color: hsl(210, 10%, 4%);
+    font-family: "Trebuchet MS", "Liberation Sans", sans-serif;
+}
+
+#gc_panel, #lxg_panel {
+    width: 400px;
+    height: 700px;
+    margin-top: -350px;
+    margin-left: -200px;
+}
+
+#tf_panel {
+    width: 800px;
+    height: 600px;
+    margin-top: -300px;
+    margin-left: -400px;
+}
+
+#conj_panel {
+    width: 700px;
+    height: 700px;
+    margin-top: -350px;
+    margin-left: -350px;
+}
+
+.grammalecte_title_bar {
+    position: sticky;
+    width: 100%;
+    background-color: hsl(210, 0%, 100%);
+    border-bottom: 1px solid hsl(210, 10%, 50%);
+    font-size: 20px;
+}
+.grammalecte_title {
+    padding: 10px 20px;
+}
+.grammalecte_label {
+    display: inline-block;
+    padding: 0 10px;
+}
+
+.grammalecte_close_button {
+    float: right;
+    padding: 2px 10px;
+    background-color: hsl(0, 80%, 50%);
+    border-radius: 0 0 0 3px;
+    font-size: 22px;
+    font-weight: bold;
+    color: hsl(210, 0%, 100%);
+    text-align: center;
+    cursor: pointer;
+}
+
+.grammalecte_panel_content {
+    height: calc(100% - 45px); /* panel height - title_bar */
+    overflow: auto;
+}