Confirm page unload when save is 5 Min+ old

src/App.svelte

@@ -31,9 +31,25 @@
       closeAllModals();
     }
   }
+
+  function handleBeforeUnload(event: BeforeUnloadEvent) {
+    console.debug(
+      "beforeUnload",
+      Date.now() - SharkGame.SaveHandler.lastSaved >= 60 * 1000,
+      Date.now() - SharkGame.SaveHandler.lastSaved,
+      60 * 1000
+    );
+    // If last save is over a minute old
+    if (Date.now() - SharkGame.SaveHandler.lastSaved >= 60 * 1000) {
+      // Annotyingly, the standardized way isn't supported, so both outdated ones will have to suffice
+      event.preventDefault();
+      return (event.returnValue = "Last save is over a minute old.");
+    }
+  }
 </script>
 
 <svelte:body on:keyup={handleKeyUp} />
+<svelte:window on:beforeunload={handleBeforeUnload} />
 
 <Modals>
   <div slot="backdrop" id="modal-backdrop" on:click={closeAllModals} />

src/shark/SaveHandler.ts

@@ -22,6 +22,13 @@ type Save = Version0Save | Version1Save;
 
 export class SaveHandler extends StaticClass {
   static readonly saveName = "sharg-save";
+  static #lastSaved = Date.now();
+  static get lastSaved(): number {
+    return SaveHandler.#lastSaved;
+  }
+  private static set lastSaved(val) {
+    SaveHandler.#lastSaved = val;
+  }
 
   static #saveInterval: ReturnType<typeof setInterval> | undefined = undefined;
 
@@ -31,7 +38,10 @@ export class SaveHandler extends StaticClass {
         clearInterval(SaveHandler.#saveInterval);
       }
       if (settings.behavior.autoSave.current !== "Off") {
-        SaveHandler.#saveInterval = setInterval(() => game.save(), settings.behavior.autoSave.current * 1000);
+        SaveHandler.#saveInterval = setInterval(
+          () => SaveHandler.save(game),
+          settings.behavior.autoSave.current * 1000
+        );
       }
     });
   }
@@ -86,6 +96,7 @@ export class SaveHandler extends StaticClass {
     );
 
     localStorage.setItem(SaveHandler.saveName, encodedSave);
+    SaveHandler.#lastSaved = Date.now();
     console.timeEnd("Done saving");
   }