Add power conversion entries and responsive nav tweaks

hdyc-svelte/src/lib/components/Calculator.svelte

@@ -13,6 +13,8 @@
   let val2 = '';
   let val3 = '';
   let activeField: 1 | 2 | 3 = 1;
+  let swapSnapshot: { val1: string; val2: string } | null = null;
+  let isSwapFlipped = false;
 
   $: has3 = ['3col', '3col-mul'].includes(config.type) || !!config.labels.in3;
   $: isTextInput = ['base', 'text-bin', 'bin-text', 'dec-frac', 'dms-dd', 'dd-dms'].includes(config.type);
@@ -24,7 +26,13 @@
 
   let paramsInitializing = true;
 
+  function resetSwapState() {
+    swapSnapshot = null;
+    isSwapFlipped = false;
+  }
+
   function handleInput(source: 1 | 2 | 3) {
+    resetSwapState();
     activeField = source;
     const result = solve(config, source, val1, val2, val3);
     if (source !== 1) val1 = result.val1;
@@ -33,14 +41,23 @@
   }
 
   function swap() {
-    [val1, val2] = [val2, val1];
-    handleInput(1);
+    if (isSwapFlipped && swapSnapshot) {
+      val1 = swapSnapshot.val1;
+      val2 = swapSnapshot.val2;
+      resetSwapState();
+    } else {
+      swapSnapshot = { val1, val2 };
+      [val1, val2] = [val2, val1];
+      isSwapFlipped = true;
+    }
+    activeField = activeField === 1 ? 2 : 1;
   }
 
   function clear() {
     val1 = '';
     val2 = '';
     val3 = '';
+    resetSwapState();
   }
 
   onMount(() => {