diff --git a/wolf3d-editor/app/src/components/SidePanel.jsx b/wolf3d-editor/app/src/components/SidePanel.jsx
index 3feb809..e35d949 100644
--- a/wolf3d-editor/app/src/components/SidePanel.jsx
+++ b/wolf3d-editor/app/src/components/SidePanel.jsx
@@ -1,6 +1,6 @@
 import React from 'react';
 import { levelLabel, LIMITS } from '@wolf3d/data';
-import { store, currentLevel, updateUi } from '../store.js';
+import { store, currentLevel, updateUi, createLevel, deleteLevel } from '../store.js';
 import { useStoreVersion } from '../hooks.js';
 import { levelStats } from '../game/stats.js';
 import { floorCodeColor } from '../game/assets.js';
@@ -39,8 +39,18 @@ export function SidePanel() {
         minHeight: 0,
       }}
     >
-      <div style={{ color: 'var(--dim)', fontSize: 11, padding: '8px 8px 4px' }}>
+      <div style={{ color: 'var(--dim)', fontSize: 11, padding: '8px 8px 4px', display: 'flex', alignItems: 'center' }}>
         LEVELS ({game.levels.filter(Boolean).length} in {game.ext.toUpperCase()})
+        <button
+          style={{ marginLeft: 'auto', padding: '0 6px', fontSize: 11 }}
+          title="Create a level in the first empty slot"
+          onClick={() => {
+            const slot = game.levels.findIndex((l) => !l);
+            if (slot >= 0) createLevel(slot);
+          }}
+        >
+          + new
+        </button>
       </div>
       <div style={{ overflowY: 'auto', maxHeight: '38%', borderBottom: '1px solid var(--border)' }}>
         {game.levels.map((l, i) =>
@@ -60,10 +70,24 @@ export function SidePanel() {
                 whiteSpace: 'nowrap',
                 overflow: 'hidden',
                 textOverflow: 'ellipsis',
+                display: 'flex',
+                alignItems: 'center',
               }}
             >
               <span style={{ opacity: 0.6, marginRight: 6 }}>{levelLabel(i)}</span>
-              {l.name || '(unnamed)'}
+              <span style={{ overflow: 'hidden', textOverflow: 'ellipsis' }}>{l.name || '(unnamed)'}</span>
+              {store.ui.level === i && (
+                <span
+                  title="Delete this level"
+                  style={{ marginLeft: 'auto', cursor: 'pointer', padding: '0 4px' }}
+                  onClick={(e) => {
+                    e.stopPropagation();
+                    if (window.confirm(`Delete ${levelLabel(i)} "${l.name}"?`)) deleteLevel(i);
+                  }}
+                >
+                  ✕
+                </span>
+              )}
             </div>
           ) : null,
         )}
diff --git a/wolf3d-editor/app/src/store.js b/wolf3d-editor/app/src/store.js
index 4f45f3d..723b5d6 100644
--- a/wolf3d-editor/app/src/store.js
+++ b/wolf3d-editor/app/src/store.js
@@ -247,6 +247,47 @@ export function setSpritePixels(num, pixels) {
   notify();
 }
 
+/**
+ * Create a fresh level in an empty slot: solid grey-stone border, floor code
+ * 6C inside, player start in the middle (the engine requires exactly one).
+ * @param {number} slot
+ */
+export function createLevel(slot) {
+  const game = store.game;
+  if (!game || game.levels[slot]) return;
+  const plane0 = new Uint16Array(MAP_WIDTH * MAP_WIDTH);
+  const plane1 = new Uint16Array(MAP_WIDTH * MAP_WIDTH);
+  for (let y = 0; y < MAP_WIDTH; y++) {
+    for (let x = 0; x < MAP_WIDTH; x++) {
+      const border = x === 0 || y === 0 || x === MAP_WIDTH - 1 || y === MAP_WIDTH - 1;
+      plane0[y * MAP_WIDTH + x] = border ? 1 : 0x6c;
+    }
+  }
+  plane1[32 * MAP_WIDTH + 32] = 19; // player start facing north
+  game.levels[slot] = { name: `New Map ${slot + 1}`, plane0, plane1, plane2: null };
+  store.ui.level = slot;
+  store.ui.dirty = true;
+  notify();
+}
+
+/**
+ * Remove a level from its slot.
+ * @param {number} slot
+ */
+export function deleteLevel(slot) {
+  const game = store.game;
+  if (!game || !game.levels[slot]) return;
+  game.levels[slot] = null;
+  store.undoStack = store.undoStack.filter((r) => r.level !== slot);
+  store.redoStack = store.redoStack.filter((r) => r.level !== slot);
+  if (store.ui.level === slot) {
+    const next = game.levels.findIndex(Boolean);
+    store.ui.level = next >= 0 ? next : 0;
+  }
+  store.ui.dirty = true;
+  notify();
+}
+
 /** Mutate UI state and notify. @param {(ui: typeof store.ui) => void} fn */
 export function updateUi(fn) {
   fn(store.ui);
diff --git a/wolf3d-editor/app/test/zip.test.js b/wolf3d-editor/app/test/zip.test.js
new file mode 100644
index 0000000..b05e6c0
--- /dev/null
+++ b/wolf3d-editor/app/test/zip.test.js
@@ -0,0 +1,24 @@
+import { describe, it, expect } from 'vitest';
+import { buildZip, readZip, crc32 } from '../src/io/zip.js';
+
+describe('zip container', () => {
+  it('round-trips entries', async () => {
+    const entries = [
+      { name: 'GAMEMAPS.WL6', data: Uint8Array.from({ length: 5000 }, (_, i) => (i * 7) & 0xff) },
+      { name: 'MAPHEAD.WL6', data: Uint8Array.from({ length: 402 }, (_, i) => i & 0xff) },
+      { name: 'dir/readme.txt', data: new TextEncoder().encode('hello wolf') },
+    ];
+    const zip = buildZip(entries);
+    const back = await readZip(zip);
+    expect(back).toHaveLength(3);
+    for (let i = 0; i < entries.length; i++) {
+      expect(back[i].name).toBe(entries[i].name);
+      expect(back[i].data).toEqual(entries[i].data);
+    }
+  });
+
+  it('computes standard CRC32', () => {
+    // CRC32 of "123456789" is 0xCBF43926 (the canonical check value).
+    expect(crc32(new TextEncoder().encode('123456789'))).toBe(0xcbf43926);
+  });
+});