Survival Defense: Zombie

We opened Survival Defense: Zombie to play a few rounds and get a feel for it, then ended up spending a whole evening on it because stage three wouldn't let us through. The setup is very tidy: a wall at the bottom of the screen and a line of zombies shambling down from the top. At a glance you'd think every round is the same.

By the time the wall's HP had dropped from 3,000 to just over a thousand, the kill counter had only crept up to 10 out of 20, and that's when we realized the game was sizing us up, not going easy on us. From that exact shortfall onward, everything the game tries to sell is aimed squarely at the button we had just failed to press.

How a round plays out, and why it's so short

The screen is vertical and split cleanly in two. The bottom half is your wall with four characters taking cover behind it. The top half is open ground the zombies pour down in waves, each always a bit bigger than the last.

You don't aim and you don't drag anything. All four characters fire upward nonstop on their own, so your job is just watching two numbers at the top: zombies killed out of the total required, and a clock running since the battle began.

Win and loss are judged bluntly, with no second chances. Hit the kill quota and you clear the stage; let the wall hit zero HP first and the screen says Failure. Our losing run ended at 2 minutes 28 seconds with 11 out of 20. The game still handed out 58 gold and a few gear pieces as if nothing had happened.

Three cards appear mid-battle, and you only get to take one

What kept us around longest wasn't the zombies, it was the skill picks. After each wave the battle pauses and the game deals three cards, each upgrading something different, and each for one specific character rather than the whole team.

Some cards add flat damage, some let a bullet pierce two more targets, some make ice bullets shatter into three smaller ones on first contact. They stack across waves, so by wave five your squad fights in a completely different way than when the battle started.

Those three cards are random, and this is where the game sets its first hook. Under the cards is a refresh button, three uses per round, but each use costs a 30-second unskippable ad. We tried it once and sat through exactly half a minute before the new set of cards appeared.

At the end of a round, the reward screen dangles a double-reward button too, three a day, also paid for with ads. To be fair, the game doesn't force anyone to press these buttons, but it places them exactly when you've just lost and feel the sting. Skip them and the rewards still land in your wallet, just half of what someone who sits through the ad gets.

A three-person lineup, with the fourth character waiting until stage 4

Outside battle, you'll spend most of your time on the character screen. The commander is fixed, while you fill the three teammate slots yourself; each teammate brings their own skill, and the game spells out the numbers clearly instead of giving vague descriptions.

Take Juli: the rolling-wheel skill deals 145 area damage, with a 15-second cooldown and a range of 240. You also get six gear slots from helmet to gloves, and every piece you equip pushes the whole team's power rating up a visible notch.

The lineup stays at three for quite a while. The fourth slot only opens when the commander reaches level 5, and leveling means fighting. The character list also stamps the requirement right on each locked face: one unlocks at stage 4, one at stage 7, one at stage 10 and the last all the way at stage 14. In other words, to get a strong team you need to clear stages, and to clear stages you need a strong team.

Stamina and patrols, two clocks running side by side

Every battle costs 5 stamina, and the stamina tank holds at most 30. So in one sitting you get six rounds and then have to wait, and each point takes about six minutes to come back, according to the countdown right under the number.

To make up for it, the game has a patrol system that runs in the background while you're away. At stage 3, patrols produce 42 gold and 3 gear items per hour, stacking up to eight hours, so when we came back we collected 336 gold, 16 character shards and 24 gear items in one go.

Gold is pocket money, for equipping gear and small upgrades. Purple gems are the expensive currency, used for unlocks, and both trickle into your wallet very slowly if you only play a little each day. The game knows this very well, and it has a few buttons ready for you, as the next section shows.

The speed-up button is where the game shows its hand

In battle there's a small button labeled x1 in the left corner. We tapped it hoping to double the battle speed and spare ourselves some watching, but what came up wasn't a speed setting; it was a sales panel called Quick Buy.

That panel sells the VIP Monthly Card for $9.99, and it lists all four things that have been bugging you so far: early access to triple speed, +20 to the stamina cap, unlimited patrols and no ads. Next to it is a one-time trial button, paid for by watching an ad.

Right after your first loss, the game piles on two more layers: a $0.99 starter pack labeled 2000 percent value, with its gifts spread over three days, then a 12-hour limited pack labeled 3000 percent. The main shop sells tickets from $4.99 for 499 tickets up to $199.99 for nearly twenty thousand.

What the mod does, and what we haven't verified yet

In VipMod, this game gets a red MOD button floating on the screen. Tap it and you get exactly one switch that bundles four things together: an invincible wall, damage multiplied a thousand times, both speed-up settings unlocked, and direct payouts on the buttons with the video camera icon.

On our very first test, before the mod's data pack had been published, flipping the switch changed nothing: the damage numbers on stage 3 stayed at 41 and 110, exactly as without it. With the current release it's a different story. Flip the switch, tap the restart button the menu suggests and head into a battle: regular zombies now drop on the first bullet that hits them, so the field stays clear where the original game would be packed.

The ad buttons changed too: the skill card refresh and the end-of-stage double reward now pay out directly without showing any ad. Two parts of the bundle we still haven't been able to verify: the invincible wall, because the wall was never attacked in the first two stages, and the speed-up settings, because the game's tutorial pushes you into a monthly VIP card trial before you ever reach the speed button.

Three things to know up front so your expectations are right:

• Turning the switch on or off doesn't break Survival Defense: Zombie, doesn't lose your save and doesn't crash the round you're playing.
• All four features share one switch, so there's no way to turn on just the speed-up or just the ad skipping.
• The first time you open the game you need a connection so it can finish downloading its own data pack; until then the switch simply waits rather than failing.

What it's like to actually play

The praise goes to the pacing. A round lasts just two to three minutes, and the skill cards are random enough that no two rounds are alike. Bullets filling the screen look great, even though the graphics are simple chibi. It's the kind of game that's perfect to open while waiting for the bus.

The annoyances are just as clear. The game needs a constant connection: lose it and you're stuck on the loading screen, unable to even reach the login screen.

On Google Play, in the store region we checked, the game held 4.8 stars from 842 ratings and over 100 thousand downloads. Those are the numbers of a game released in July, not a blockbuster. The high score is partly earned, but it comes from new players, the ones who haven't yet reached the point where stamina and ads start wedging themselves between rounds.

So who should play it?

If you like tower defense with a roguelite twist, short rounds and a different skill build every time, Survival Defense: Zombie is an easygoing, free game to try. Just accept that after about six rounds in a row you'll have to get up and do something else for a while.

And if you gave up at those 30-second ads, the mod now takes care of them: the refresh and double-reward buttons pay out without a video, and regular zombies fall in one hit. The locked speed-up button is the one part we still can't vouch for, and we'll say so right here once we've measured it.