Slime Castle — Idle TD Game

Thirty waves a chapter, and I fell on wave three

I opened Slime Castle thinking it was another tower defense game to tap at for fun, since the green slime guarding the castle gate looks far too sweet to ever lose. The first battle really was easy: monsters trickled in and I just sat there tapping attack upgrades.

On wave three, an axe-wielding brute twice the size of the earlier monsters walked into the frame. My attack was only twenty at that point, and I'd long since spent all the silver earned in the battle. The castle gate broke less than ten seconds later.

The screen said defeat, noted that I'd stopped at wave three of chapter one, then paid me 198 gold in wages. The whole game loop is captured in that moment: here, even losing earns you a paycheck. I tapped confirm and went back to the main screen.

How a battle plays out

You don't place towers or drag units; the whole battle is one slime standing still on a stone pedestal on the left, shooting to the right. Monsters come in waves, each bigger and tankier than the last, and the red orb in the bottom-left corner is the gate's HP. There's no second lane to split your attention.

What you actually control is the bottom half of the screen, with four upgrade slots: attack, attack speed, crit chance and crit damage multiplier. Every tap costs a bit of silver, and the next tap always costs a step more than the last.

Silver flows in on its own over time and with every monster you kill, so a battle becomes a tidy budgeting problem. Upgrade early and you're strong early but broke; save too long and by the time you need it, it's too late to recover. It took me a few losses to get the rhythm.

In the middle of the upgrade panel are three multiplier buttons, x1, x10 and x50, for bulk buying once your balance is large, to save your fingers. On the right of the battle area there's also a speed button, which in the regular version only toggles between x1 and x2. That button turns out to matter later.

The gold you bring home from defeats is what keeps you playing

Silver only lives for one battle and is gone when it ends, while gold follows you back to the main screen. Gold goes into the Talents board, where every stat you buy comes with you into all future battles. That's the game's entire progression.

The board starts with four familiar lines, but there's always a locked line at the bottom with its own price, such as unlocking the attack range talent for four hundred gold. Pay it and two new lines sprout, followed by another locked line priced at six hundred.

So the early game feels like running into a wall, bouncing off, picking up gold, then running into it again with slightly better stats. A losing battle in chapter one lasts only about a minute, so the loop spins fast enough that it never gets boring. In one evening you can get through a few chapters.

Slimes, gear and an endless collection board

Clear chapter one and the game unlocks a pile of new things at once, the most eye-catching being the slime board. Arp, the slime you start with, is only B rank; behind it is a long row of grayed-out A and S ranks, each needing fifty shards to unlock. Shards drop from chests and daily quests.

Each slime has its own level track up to one hundred, with milestone rewards at levels ten, twenty-five, fifty, seventy-five and one hundred. Each level needs blue crystals, which only drop when you clear a chapter and can't be bought with gold.

Alongside that are four gear slots, weapon, armor, helmet and accessory, with gear coming from chests in the shop. My first armor piece added a flat sixty HP, and it also listed a four-piece set for collectors to chase. Only the full four-piece set unlocks its special effect.

Where the game holds out its hand

Gems are the third currency and the hardest to earn, since the shop only gives you twenty-five a day. A regular chest already eats sixty, and the ten-open bundle of the mystic chest is priced at 2,200. Gems are also the fastest way to open chests.

Simple division shows the wall right away: saving up for that one ten-open takes nearly three months of claiming the daily gift without fail. The top-up screen lists six tiers from two hundred to twenty thousand gems, and every tier carries a double-bonus label. That tells you pretty clearly what the publisher has in mind.

There's also a one-time chapter one pack advertised at six hundred percent value, with gold, three hundred gems, a hundred shards and four keys. On our device the price fields of the real-money packs were blank, meaning the real-money purchase route wasn't usable.

The mod removes exactly what stopped me in chapter one

The MOD menu floats inside the game as a round red button; tap it and you get five switches, and to be safe you should turn them on before launching the game. The two switches we got working end to end are Freeze resources and Unlock adventure privileges. We turned on all five and then restarted the game.

With the first switch, I went into the Talents board holding 495 gold and kept buying until nothing priced under that was left. Combat power jumped from 1,382 to 29,000, while gold stayed right at 495.

Same story in battle: I tapped the attack upgrade twenty times in a row and the stat went from 82 to 254, while silver not only didn't drop but actually went up. After fully closing the game and reopening it, everything was still there, so this is real spending, not a pretty number that flickers by. We do this step because screens lie a lot.

The second switch turns the speed button from two settings into five, and at x5 a thirty-wave chapter wraps up in a few minutes. Thanks to that, on that run I cleared chapter one without the castle gate losing a single point of HP.

A few things to know up front so your expectations are right:

• Freezing doesn't mean you can buy everything: anything that costs more than your current balance stays grayed out and won't respond.
• The blue crystals used to upgrade slimes aren't covered; I upgraded exactly one level and they dropped right away from three to two.
• Of the other three switches, the monthly card one works (one tap claimed 470 gems from both cards), the Pass one is currently broken, and the ad one can't be proven, because no ads ever loaded in our tests.

What it's like to actually play

The graphics are pleasant. The game doesn't force you to sign in either; the settings just warn that without signing in, your data is lost if you uninstall the app. You can start playing right away without an account.

The biggest drawback is that you must be online: the loading screen stops at sixty percent and reports that it can't get the server time as soon as the connection drops. So don't expect to start a single round on a plane or down in a parking garage.

On the plus side, the online part gives you things to do: a seasonal arena now on season seventy-four, leaderboards and a global chat box that sits at the bottom of the main screen. On the app store, the game held 4.8 stars from 67,000 ratings and more than a million downloads. That chat runs mostly in English.

So who should play it?

If you like compact tower defense, a few minutes a round, with no tower layouts to memorize, this is an easygoing pick for when you're waiting around. The lose, get stronger, lose again loop is very smooth, and you always see the numbers tick up after every defeat. Weaker phones can run it thanks to a low graphics option.

And if you quit right where the Talents board showed a four-hundred-gold lock while your wallet held one hundred ninety-two, the two switches above remove exactly that. You still have to play and still have to earn; you just don't have to grind chapter one for the tenth time to afford it.