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Tips and strategy: how to hold the city in City Defense

The key is knowing where enemies will go and covering those spots with towers on tall buildings. Then upgrade your towers, protect the buildings they stand on, and save dynamite and airstrikes for when they really help. Here are nine tips based on the game's rules and on tests with computer bots.

Updated September 30, 2026

1. First, find out where the enemies will go

Enemies take the shortest route along real streets, sidewalks and passages. Sometimes the shortcut runs through a building – an arcade or passage you can barely see from the street. In Brno, one route leads straight onto náměstí Svobody this way. Leave it uncovered and you will lose fast.

• When you pick a tower, the preview shows which streets it would cover from that roof. Enemy routes are drawn with a thicker line.
• Press X to make buildings see-through and spot streets and enemies behind them.
• The M key (or “Map” at the top right) switches to the top-down view with all enemy routes at once.

2. Build on tall buildings where routes meet

Range grows with roof height: the laser reaches 150 m plus 2.5 m per meter of height, so about 212 m from a 25-meter building. The best spots are where several routes merge into one street shortly before a gate – one tower there can fire at every stream of enemies.

Direct-fire towers (machine gun, laser) need a view of the street. A low building in a narrow street often can't see past the house next door. Before you build, look at the eye tag on the see-through preview: a low percentage (a red tag) means buildings hide most of the routes in range – try a taller or more open roof, or the edge of the roof closer to the street. Ballistic towers don't need a view – they fire over the roofs.

3. Mix direct and ballistic towers

• The machine gun ($100) is cheap and fast – the ideal first tower near a gate.
• The laser hits every visible enemy along its beam, so it shines over a long, straight street.
• The mortar and howitzer have a dead zone (35 and 50 m) and can't hit anything close. Place them further back and leave close defense to machine guns.
• Ballistic blasts damage buildings. A level-3 mortar or a howitzer can bring down a building your own tower stands on.

4. Upgrade – it pays off

Each level adds 40% damage, 15% faster reloading and 15% range. Level 2 costs 70% of the tower's price, level 3 costs 120%. In the game's balance test on the Brno map with the new enemy types and bosses, a bot that upgrades its towers won in all three test runs. The same bot without upgrades lost in wave 10 every time. Between waves, you can tell which towers can be upgraded right now by the bold marker with an amber arrow.

5. Rubble as a weapon: use dynamite wisely

You get 2 dynamite charges per mission. A collapsed building buries the street within 8–18 m, depending on its height.

• Walkers and Armored enemies cross rubble three times slower, or walk around it. A longer route means more time under fire.
• A blockage only delays enemies – it never seals the route. When climbing over the rubble is faster than a detour, they climb over it.
• The preview shows which stretches of street the rubble will bury. If no enemy route goes there, save the charge.
• You can't blow up a building with a tower on it, so don't build on a house you plan to demolish later.

6. Protect the buildings your towers stand on

Shooters, heavy shooters and sappers attack buildings that carry towers. When a building falls, its tower is lost and you only get half your investment back.

• Bigger, taller buildings last longer – a building's hit points grow with its volume (150 to 1,600).
• Towers defend themselves: they target whoever is attacking their building first. Towers that cover each other hold out longer.
• Stop sappers before they reach the building – a charge goes off after 3 s and deals 250 damage.

7. Save the airstrike for a crowd or a boss

An airstrike ($150) deals 200 damage to enemies within 20 m and can be called during a wave. It then recharges for 20 s. It works best on a crowd stuck at rubble or on a boss. Careful: buildings within 15 m of the impact take 400 damage – the game warns you if one of your own towers might fall.

8. Prepare for bosses in advance

• Crusher (Brno, wave 5) walks over rubble without stopping – a blocked street will not slow it down. It wears down buildings within 10 m and brings down the building its path runs through (the pink “Passage through a building!” marker in the top-down view) – do not build towers on it. Towers on weak or already damaged buildings along its route may fall – kill it fast, for example with an airstrike.
• Besieger (Brno, wave 10) shells buildings with towers from 150 m. It stands still while firing, which makes it an easy target for mortars and howitzers.
• Shieldbearer halves the damage taken by enemies within 20 m. Take it out first.
• Summoner releases two Runners every 6 s. The longer it lives, the more enemies come at you.

You can find out where a boss is by clicking or tapping its bar at the top – the camera flies to it and follows it for a while. Handy when you want to aim an airstrike at it.

9. No rush between waves

A wave only starts when you start it. Take your time with building, upgrades and dynamite. During a wave you can speed the game up to 2× or 4× – and slow it back down when things get tense.