rename Editor -> ExprBlock

src/ExprBlock.css

@@ -0,0 +1,39 @@
+.editor {
+  padding: 2px;;
+}
+.editor.error {
+  border: 1px solid red;
+  display: inline-block;
+}
+.editor.unknown {
+  border: 1px dashed dodgerblue;
+  display: inline-block;
+}
+
+*:hover:not(:has(> *:hover)) {
+  /* useful for debugging: */
+  /* border-width: 2px !important; */
+}
+
+.offending .error {
+  background-color: transparent;
+}
+
+.typeSignature {
+  display: inline-block;
+  z-index: 1;
+}
+
+.editor:hover > .typeSignature {
+  display: inline-block;
+}
+
+.commandInput {
+  width: 30px;
+  margin-left: 10px;
+}
+
+.keyword {
+  color: blue;
+  font-weight: bold;
+}