Nitropolis 4

(ELK Studios) Slot Review

ELK Studios

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Nitropolis 4: Slot Overview

As the game says, 'Welcome to the freak show' players, and if you've been following the series, this will be your fourth nitro-fuelled freakshow so far. We're talking about none other than ELK Studios' vision of a future sans humans, where animals run the show in Nitropolis 4. So far, each release in the Nitropolis range has been an adrenalised, in-your-face, potentially highly explosive experience, and the expectation is of the same, plus a little (or a lot) more. A cursory look over the paytable would seem to confirm the cacophony of action is back, where features like Nitro Boosters, Nitro Multipliers, Nitro Reels, Avalanches, Big Symbols, and two bonus games compete with each other for players' attention.

Part three saw the pups, rats, and cats flee the city to a toxic seaside, but in Nitropolis 4, the crew are hard at work. Their gainful employment appears to revolve around resource extraction at sea, perhaps dredging up the green Nitro which fuels their cars. Not sure, yet it's a spot that gave the studio a chance to create some more exciting dystopic visuals, to let the critters loose in to see what's up. Another part of Nitropolis' success has been its audio, and once again, Nitropolis 4 does not let us down, being an absolute mash-up of bleeps, voiceovers, and heavy-duty industrial tunes not a million miles away from something Trent Reznor or Rob Zombie might have done. Mix it all together, and the scene is set for some more Nitro-styled chaos. Bring on the gameplay.

Nitropolis 4 slot
Nitropolis 4 slot - base game

But first, some housekeeping. This means choosing whether to bet 20 p/c to $/€50 per spin or to activate the X-iter and play via one of the five feature buy options found there. Either way, players are looking at a highly volatile experience with a theoretical return value of 94%. Hit spin and the grid's default layout is 6-reels, holding 4 symbols each, providing 4,096 ways to win. However, Nitro Reels and the general expanding reel dynamic can quickly pulverise those numbers, particularly ways to win, as has been seen in previous games.

For the most part, Nitropolis 4 pays right to left starting from the first reel, but when the Both Ways feature is active, wins also form from right to left, starting from the sixth reel. When it comes to normal pay symbols, at least three are required to create a winning way. For the lows, we get J-A card ranks; the mids contain four gang logos, while the highs are four character symbols. Hitting a six-of-a-kind win awards 0.3x for the royals, 0.8-1x the bet for the logos, or 1.25 to 3 times the stake for a premium win. The spiky mine tile is wild, appearing in all six reels. Wilds substitute for any pay symbol and are worth the same as the highest-value symbol when making wild wins.

Nitropolis 4: Slot Features

Nitropolis 4 slot
Nitropolis 4 slot - free spins

Here's where things start to heat up, and being a fully decked-out ELK Studios slot means there is a lot to cover. Let's start with the basics, which is the Avalanche mechanic. When wins form, they are removed from the board and replaced by symbols dropping. An additional reel is also added at the top, up to a maximum of 8 rows high. Nitro Reels and Nitro Multipliers that are part of a win respin during this process. Avalanches keep lanching until no new winning combos hit.

Big Symbols

Super symbols 2x2 in size or Mega Symbols of 3x3 in size may appear on any spin or symbol drop. Any pay symbol or the wild can land as a Big Symbol.

Nitro Reels

Nitro Reels take up two positions on the board and land on any reel. Each Nitro Reel contains 4, 6, 8, 10, or 12 regular-sized payout symbols. Big Nitro Reels cover six positions and contain 2, 3, 4, 5, or 6 2x2 payout symbols.

Nitro Multiplier

Nitro Multipliers also cover two positions, though they count as one symbol, and multiply all wins in view. It can contain values of x4, x6, x8, x10, or x12, and when more than one is in view, they are multiplicative.

Nitro Booster

Above the grid are two displays which may award Nitro Booster modifiers. There are 8 possible effects. These are:

  • Redrop – when there are no more wins, Bonus symbols and Nitro Reels are held while all other symbols are replaced with new ones.
  • Both Ways – wins pay both ways on the grid.
  • Garbage Collect – random symbols are removed from the grid, causing an Avalanche.
  • Max Rows – the grid is expanded to its full 8-row height.
  • Nitro Appear – a random-sized Nitro Reel is placed on the board.
  • Nitro Wild – a Nitro Reel already in view will be filled with wilds. If no Nitro Reel exists, this feature is held till one appears or the game round ends.
  • Nitro Upgrade – a Nitro Reel in view has its value increased. If no Nitro Reel exists, this feature is held till one appears or the game round ends.
  • Nitro Match – an existing Nitro Reel is matched to another symbol in view to create a win. If a winning match is not possible, the chosen Nitro Reel will be matched with an adjacent Nitro Reel; if that's not possible, it will be matched with the highest adjacent symbol. If no Nitro Reel exists, this feature is held till one appears or the game round ends.

Bonus Game

Landing 3, 4, 5, or 6 bonus symbols awards 8, 12, 16, or 20 free spins – both in the base game as well as when free spins are already active. During free spins, Nitro Reels are sticky until the feature ends. Also, each win increases the safety level by one row, and the next free spin fills the grid to the current safety level, maximum of 8 rows. If one of the triggering symbols is a Super Bonus symbol, then the Super Bonus Game is awarded. In this round, Max Rows and Both Ways is always active.


The X-iter function allows users to play the game in these five modes:

  • Bonus Hunt – 2x the bet for a spin with more than double the chance of triggering the bonus game.
  • Nitro Booster – 10x the bet for a spin with two features from the Nitro Booster.
  • Super Spin – 25x the bet for a spin with Max Rows and Both Ways active.
  • Bonus – 100x the bet for guaranteed entry to the bonus game.
  • Super Bonus – 500x the bet buys access to the Super Bonus Game.
Nitropolis 4 slot
Nitropolis 4 slot - feature buy menu

Nitropolis 4: Slot Verdict

Making it to a trilogy is one thing; pushing a series out to part four or beyond shows some real staying power, and Nitropolis 4 reiterates why the range is such a crowd-pleaser. First off is the highly immersive game world, where ELK Studios turns up the development dial each time to make its Nitropolis environs drip from the screen. Animals running a dystopic world might seem odd, but it lends humour while giving the studio plenty of opportunity to provide players with an absorbing sensory experience. This all returns for Nitropolis 4, which drags in the willing, kicking and screaming as deeply as any of the previous three have.

Once in, the game has a long list of ways to entertain players while they are there. The shift from part 3 to part 4 wasn't as seismic as the shift from Nitropolis 2 to part 3 was in lots of ways, though there's a progression here. Much the same way as, say, Black River Gold kind of felt like it progressed in a more subtle way mechanically rather than in leaps and bounds. Speaking of Kane, the two popular series feel like they are getting closer together, what with the reel expansion/safety level similarities, but they're vastly different in many other areas too. For one, the mayhem levels in these Nitropolis games can be off the chart, with masses of modifiers going on, Avalanches, and the surreal number of ways to win that are achievable via the Nitro Reels. If you like big numbers, busting out a calculator to work out Nitropolis' theoretical possibilities should be right up your street. If ELK Studios keeps this up, we might have to make use of Knuth's up-arrow notation to represent the value.

What's easier to represent is the game's RTP, arguably its most disappointing factor, which is not an unusual assessment of ELK Studios' games of late. If that's not an issue, though, and you're in the mood for some reel-bound havoc, then grip the wheel tight because Nitropolis 4 delivers just as much of this as any other in the series.


Though more of a sidestep than a step forward, Nitropolis 4 is as chaotically charged as a fan of the range could ask for.

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