Nitropolis 4 review
Nitropolis 4 arrived from ELK Studios on 23 February 2023 and carried on the series about a crew of animals who drill for nitro. What defines it are two Nitro Booster screens above the reels, multipliers that multiply each other, and five paid X-iter entry modes from 2x to 500x.
An oil rig instead of a holiday
The setup is brief: after a well-earned rest the crew is ready for action. The friends spot a disused offshore oil rig where nitro can be drilled with ease. Holidays are over, and it is time to pack up and drill. The slogan reads eat, sleep, drill, repeat.
The official art gathers the whole team: a stern doberman with red eyes, a pug in a diving suit, a mouse in a yellow hard hat with a “Boss” badge, a hairless cat and a seagull perched on a sea mine. A logo with a green number four glows below them. In the game two screens hang above the reels, and flasks with multipliers appear on the grid. The word “roughneck”, as the studio explains in its fun-fact section, names a rig worker, someone doing hard manual labour.
Two screens above the reels: Nitro Booster
The screens above the playing field randomly fire Nitro Booster features on the main reels. The studio lists eight possible features: Max Rows, Garbage Collect, Nitro Reel, Nitro Wild, Nitro Upgrade, Nitro Match, Redrop and Both Ways.
The game page offers no detailed description of each feature, only the names. Judging by the names, Max Rows opens the reels to full height, Redrop makes symbols fall again, and Both Ways lets wins count from both directions; the exact rules should be read in the help window inside the game. The main consequence is different: much of the base game’s edge is stored in these screens. A spin without a feature is ordinary, while a spin with two features departs from it more sharply than a bonus in some slots departs from the base game.
Nitro Multiplier: multipliers that multiply each other
The Nitro Multiplier multiplies any win in view. The key detail is that several of them multiply one another instead of adding up: three 5x multipliers would give 15x if added and give 125x when multiplied, nearly nine times more. The studio publishes no list of possible multiplier values. So the ceiling in such a game is reached not through a long chain but through several multipliers on a large win.
The phrase “any win in view” means a multiplier is not tied to one combination. If it is visible on screen, it works on every win of that spin, including small ones that would otherwise be very modest. When judging a spin, count not only the symbols but also the flasks beside them.
Free spins and sticky Nitro Reels
Three or more Bonus symbols open the free spins. The studio names no exact spin count on the game page; it has to be read in the in-game help rather than imported from other games in the series.
Nitro Reel and Nitro Wild belong to the Booster set, and in the free spins every Nitro Reel turns sticky. Sticky means the reel persists from spin to spin and accumulates its effect. For the bonus that matters: a Nitro Reel landed early in the round keeps working for many spins.
Super Bonus: max rows and wins both ways
A combination of Bonus and Super Bonus symbols starts the Super Bonus Game. It is played with Max Rows and Both Ways switched on: the grid opens at full height at once and wins count both ways. It is the heaviest mode in the game, and no accident that it sits on top of the X-iter ladder at 500x.
At the start the six-by-four grid gives 4,096 ways, four rows to the sixth power, and with Max Rows the studio speaks of “millions”. The exact maximum number of rows and ways is not named in the materials, but in Super Bonus the grid is taller and the ways are more numerous than in any other mode.
X-iter: five entry modes from 2x to 500x
X-iter is a platform feature of ELK: a set of ready-made modes that let you jump straight into the part of the game you want. The modes depend on the particular slot, and per the studio they need no extra integrations. In Nitropolis 4 there are five.
| Mode | Price | What the studio’s description says |
|---|---|---|
| Bonus Hunt | 2x | more than double the chance of a bonus |
| Two-screen mode | 10x | the label on the icon is not printed |
| Super Spin | 25x | details are in the in-game help |
| Buy Bonus | 100x | direct entry into the bonus |
| Super Bonus | 500x | Super Bonus with Max Rows and Both Ways |
The price of each mode is clear, while the content is described sparingly: the studio explains only the outer options in any detail. The 500x mode guarantees entry into Super Bonus, not a result. In Bonus Hunt a spin costs twice as much while the bonus chance more than doubles, so the average price of a bonus in bets comes out only slightly lower than normal: the mode saves time more than money. The RTP of the bonus buy modes is not published separately, and it cannot be assumed to equal the return of the main game.
The modes belong to the studio platform, but each operator switches them on for itself. In some countries bonus buying is banned or restricted, and then the set of entry modes shrinks or disappears.
A 94.0% RTP and a 50,000x ceiling
The studio data sheet gives an RTP of 94.0%. Rare for a popular game, the return sits two percentage points under the familiar 96%: that is how the game pays for a high ceiling and rich mechanics. An operator may run its own configuration, and the rules window inside the game shows which version is live. ELK does not publish the split of RTP between base game and bonus or the bonus frequency: its data sheet carries a minimal set of numbers.
The data sheet writes the ceiling as Max win 50,000x bet, and beside it stands a maximum exposure of 2,500,000 EUR. These are two entries of one fact: 50,000 times the top stake of 50 gives exactly 2.5 million, not a ceiling for any stake. A particular casino may set its own payout cap, and the studio does not give the probability of the ceiling.
What 18.1% and 8 out of 10 mean
With an 18.1% hit frequency a win arrives about once in 5.5 spins, and assuming independent spins, five in a row without a win happen about 37% of the time, ten about 14%. Volatility of 8 out of 10 on the studio scale means payouts are uneven but not at the very edge of the scale.
The studio gave Ecuador Gold the same volatility grade of 8 out of 10, yet the numbers look completely different: Ecuador Gold has a 96.1% RTP, a 24.4% hit frequency, a 2,500x ceiling and a maximum stake of 100. Nitropolis 4 pays less often and returns less, while its ceiling is twenty times higher. That is why “8 out of 10” alone says little: the ceiling and hit frequency have to be read beside it.
The Nitropolis line: what changed
| Game | Release | RTP | Ceiling |
|---|---|---|---|
| Nitropolis 3 | 2022-04-05 | 95% | 50,000x |
| Nitropolis 4 | 2023-02-23 | 94.0% | 50,000x |
| Nitropolis 5 | 2024-07-23 | 94.0% | 50,000x |
Nitropolis 4 came out less than a year after the third part: the ceiling stayed the same and RTP dropped a point. For players who want the classic scheme, Nitropolis 3 remains the closest alternative, while Nitropolis 5 kept both the ceiling and the return of part four. Another ELK Studios release, Pirots (7 March 2023), also runs at 94% RTP, but with a different style and a 10,000x ceiling.
Devices, languages and the demo
The game runs on phones, tablets and computers, the engine uses Canvas and WebGL and adapts to the device. The desktop recommendation is a 1600×900 window, with a 16:9 shape kept when scaling. The game follows the Mobile First principle, so the X-iter interface and the Nitro Booster functions are designed for a touch screen. Among the interface languages listed are Russian, English, German, French, Japanese, Lithuanian and many others; there are many currencies too, roubles and hryvnias among them. The demo launches straight from the game page on the studio server and needs no registration.
