About › Tower defense in your own city

Tower defense in your own city: a mission editor guide

In City Defense you can set up a mission anywhere in the world in a few minutes, using the editor built into the game – no account, no download. Find the place, let the game propose the defended area and enemy spawn points, pick a difficulty, then play the mission or share it as a link. Here is how, step by step.

Updated September 30, 2026

Before you start

• Open the editor with the “Create your own mission” button on the start screen (a shorter label on a phone), or go straight to citydefense.app/?editor.
• The place needs streets and buildings in OpenStreetMap. That is true almost everywhere in cities; rural areas may be mapped more sparsely.
• The editor works on a computer and on a phone. On a phone held upright the wizard sits at the bottom of the screen – in the area and spawn step it folds down to a strip so the map stays free; drag the strip at its top or tap it to open it again.

Step 1: Find the place

Type an address or place name and press Enter (the search uses Photon on top of OpenStreetMap data and shows up to 5 results). You can also use “My location” – the browser only asks for your location after you press it – or click the map. You can then also drag the center of the play area (the amber ring) with the mouse or a finger – on a phone the wizard is only half open in this step so that the center stays visible; the search field opens it fully.

Then choose the size of the play area: 300 to 1,000 m in 50 m steps; the default is 600 m. A smaller area loads faster and is easier to read. “Continue” loads the map tiles and proposes a defended area and spawn points.

Step 2: Adjust the defended area and spawn points

The game proposes a defended area with 4 to 8 entrances: the nearest pedestrian area within 50 m of the center (a square or pedestrian zone); a huge square with many entrances is cut down by a circle around the center. If there is no suitable area, it uses a circle with a radius of 20–60 m. The editor counts entrances the same way as the game's “Where they got through” summary after a game: gates of one street are one entrance, and so are unnamed gates closer than 20 m to each other. It places spawn points on the edge of the play area – in up to five directions, each with the shortest route to the defended area.

• Drag a vertex of the area or a spawn point to move it.
• “+” on an edge adds a vertex (on a short edge it appears only after you zoom in); clicking the map adds a spawn point (invalid ones are not added).
• Tap (or click) a vertex or spawn point to select it, then delete it with the “Delete” button next to “Continue”; on a computer, a right-click deletes it straight away too.
• The row “Spawns 5 / 20 · tap the map = another spawn” (“click” with a mouse) shows the number of spawn points and tells you how to add another – even in the collapsed wizard on a phone.
• If you drag a vertex across another edge of the area, the editor reorders the vertices itself so the area does not cross itself.
• “Suggest again” restores the game's proposal. The limit is 64 vertices and 20 spawn points. With more than 12 entrances the editor warns in orange that the mission will be very hard.

Step 3: Pick the difficulty and look

Bosses are shown right under the preset: type and wave, “Add boss” and “Remove”. Several bosses in one wave arrive one after another – two after a third and two thirds of the wave, three after each quarter. Under “Advanced” you can set the numbers yourself (1–50 waves), choose enemy types, the enemy look (the “Enemies” choice), the “Historic center” preset (cobblestones instead of asphalt) and the regional look of the city. Finally, give the mission a name; a description and an author name are optional.

Step 4: Play, bot-test, save and share

• “Try it” starts a normal game. “Back to editor” returns you to editing. Between waves (not during one) you can pause the game with “Edit spawns” and add, move or delete spawn points – on a computer the button sits next to “Back to editor” and in the ☰ menu, on a phone in the ☰ menu. “Continue game” then carries on without a restart: towers, money, lives and the wave stay, and the new spawn points are written into the mission in progress.
• “Test with a bot” lets two computer players play the mission and labels it Easy, Normal, Hard or Very hard based on the result. It is an estimate, not a guarantee. The Brno mission test takes about 35–40 s on a fast computer, longer on slower computers and up to 1.5–2.5 minutes on a phone; missions with many waves take longer still. The editor stays usable and the test can be cancelled at any time.
• “Save” adds the mission to the “My missions” list in this browser.
• “Share” copies a link (on a phone it opens the share menu). Whoever opens it can play the mission or edit their own copy.
• Back to a paused game. “Back to editor” only pauses the game – even mid-wave. If you then change only the name, description, author, or the spawn points between waves, step 4 offers “Continue game”: the game goes on exactly where it stopped. “Play from the start” restarts it. After any other change (place, defended area, difficulty, enemies, look) the editor tells you why and the game starts from wave 1.

A mission with a red check (no gate, no valid spawn point, street network that doesn't reach the area) cannot be played, saved or shared. The editor shows the reason next to the relevant step.

Tips for a good mission

• Fewer entrances make a more playable mission. The Brno mission defends a 30 m circle with 6 entrances. The whole pedestrian zone of náměstí Svobody has 9 entrances, so the editor cuts it down with a circle to 8. The bot test label is an estimate from one game of two bots. A large area with the Normal preset can come out as Very hard – the Summoner in wave 8, which summons Runners, is the main trouble.
• Put spawn points on different sides. Enemies from one direction are easy to cover; from four directions it becomes a real challenge.
• Run the bot test before sharing. If even the upgrading bot can't win, add money or lives, or shrink the defended area.
• Turn on “Historic center” in old town centers – the ground gets cobblestones and the city looks more authentic.

Where missions are stored

“My missions” live only in your browser's storage. The game has no accounts and no mission server. If you clear your browser data, the missions are gone – a shared link is your backup. The link carries the whole mission in the part of the address after #, which is never sent to the server. A mission only remembers the place and the rules; streets and buildings are rebuilt for each player from current map data.