Crafting Candy Crush’s difficulty: Blockers, level design, AI and the "complexity staircase"

• Crush & Tell's sixth episode features Candy Crush senior product manager John Davies, who discusses level design, blockers, and difficulty.
• We discuss new blockers, introducing them to players, and the role of AI in the design process.

The final episode of King’s vodcast-style Crush & Tell series is out, giving fans a peek behind the curtain at Candy Crush’s blockers, their origins and how the challenge they add makes the game more fun.

Now, we pull that curtain back further with senior product manager John Davies, who speaks about Candy Crush’s design process, its various blockers and how they interplay with overall level difficulty. We also talk more broadly about crafting new puzzles, reaching beyond Level 20,000 and the increasing use of AI in the design process.

"We introduce blockers to players on a ‘complexity staircase’," Davies begins. "This means newer players early in the game see simpler blockers and more experienced players who’ve passed more levels get to tackle more complicated ones.

"Earlier blockers often increased difficulty by simply restricting space or absorbing moves, which worked well in the game’s early years. Over time, the philosophy has shifted toward blockers that create interesting choices rather than pure obstruction.

"Modern blockers are designed to interact with objectives, special Candies and board layouts in ways that reward planning and understanding, making the difficulty and challenge feel more thoughtful."

Blocker behaviour

Candy Crush blockers span a range of behaviours and are key to helping the match-3 giant feel fresh almost 14 years on from release - providing a variety of challenges with different requirements to clear them.

Some are simple to overcome, cleared by matching nearby Candies of any kind, while others require a "special" type of match or a booster to clear. Furthermore, some can be swiped or fall down the board as spaces clear, while others are fixed in place. Naturally, these provide a ranging level of challenge and require different strategies from players.

"We also enjoy mixing up game board shapes with blockers of different sizes, blockers that require a set number of colour-specific matches, and blockers that transform when you interact with them," Davies shares.

"New levels typically feature a mix of both recent and long-established blockers. New mechanics need enough visibility for players to learn and become comfortable with them, but Candy Crush relies on its full blocker library to maintain variety and avoid repetition. Designers are also mindful that not all players encounter new blockers at the same pace, so a balanced mix helps keep levels readable and fair."

On the subject of new blockers, Davies notes that the Mal-O-Matic has become widely discussed since its debut in 2025. It’s a blocker that dispenses string, designed to look like marshmallow or candy floss, which players must make matches against to shorten one tile at a time. Once the string column is fully shortened, the blocker is destroyed.

Davies explains that the Mal-O-Matic was introduced gradually, not universally, so that the team could observe performance data and the perceptions of players before it finally became a regular part of level design.

"Making a blocker’s behaviour and appearance feel aligned is extremely important, because that’s how players build an intuitive understanding of how the game works. If something looks heavy, fragile, or volatile, players expect it to behave that way when they interact with it," he adds.

"Achieving that cohesion requires close collaboration between gameplay designers, artists, and UX specialists, particularly in a game as visually dense as Candy Crush. Clear visuals, readable animations, and strong feedback help players understand what’s happening without needing explicit explanation."

We ask how frequently the team makes new blockers, and Davies answers that there’s no "fixed cadence". Rather, new blockers are typically developed when the current roster can’t fully support the types of levels designers want to create - be it a denser board layout, a more complex objective, or a new type of player decision.

"Importantly, any new blocker has to earn its place by offering a distinct behaviour or interaction, rather than simply acting as a variation on something players already know," Davies clarifies.

"Some years see a meaningful new addition, while others focus more on refining and rebalancing the existing mechanics rather than expanding the blocker catalogue."

And, rebalancing other mechanics can also have a knock-on effect for blockers. The recent overhaul to Candy Crush’s Swedish Fish booster, for example - which granted more intellectual behaviour and greater effectiveness against certain blockers - has made some early levels easier than originally intended.

"This influenced how designers think about Fish when building new levels and has encouraged us to think about how players can use Fish as a strategic tool," says Davies.

"We don’t want any level experience to feel trivially easy."

Challenge and change

Candy Crush players range from casual to hardcore, some preferring to take a laidback, relaxed approach to the game and others in it for the challenge.

Senior game designer Mick Heijkens recently told us about navigating a game with this "spectrum of flavours", where a surprising number of casual and competitive players do keep up with the latest updates.

For this reason, we now ask Davies how the latest levels are designed and how difficulty is balanced in the context of a player’s rising skill - made for those with 20,000 levels already behind them.

"Designers assume that long-term players have spent more time in the game and over time have developed a deeper understanding of the game’s systems," he reveals.

"Difficulty at that stage often comes from more intricate objectives, tighter constraints, and more complex board layouts. The goal is to respect player mastery while ensuring levels still feel fair and easy to understand for the player."

He adds that such high-numbered levels can be more challenging, but it’s not as simple as overflowing the board with more blockers, and game design between levels isn’t as straightforward as each level being harder than the one before.

"There’s a deliberate effort to vary difficulty rather than constantly increasing it. It’s common for a particularly challenging level to be followed by something lighter, giving players a sense of variation and momentum," he says.

Davies reveals that most levels are designed with a clear intent: the objective, approximate difficulty, and a player’s experience level are already decided at the beginning of the process.

He shares that when crafting a more challenging level, designers tend to use blockers that require prioritisation and decision-making. This is because the difficulty comes in players strategising which to tackle first, which is "more engaging" than grinding resistance against blockers with multiple layers.

"Automated testing is an important part of the level design process," Davies adds.

"We use bots to simulate large numbers of plays to help us estimate difficulty before we release new levels to players. But this is strictly an AI assistant: it’s best seen as a support tool rather than a replacement for human judgement.

"Bots are excellent at identifying outliers and predicting pass rates, but they don’t always capture how a level feels to play, which is why human testing and live player data remain crucial to our process."

AI is being used increasingly in Candy Crush to generate draft levels too, effective at speeding up repetitive, time-consuming tasks. The tech also helps improve older levels and allows designers to explore different combinations at scale. But Davies assures creative judgement still relies on human designers, whether that’s crafting an interesting blocker or a memorable level.

"AI works best when it enhances the creativity of our level designers," he says.

Behind the scenes - and in the public eye, in the case of Fish - King has been busy modernising older systems so they can continue to work well alongside new mechanics. Entering into 2026, Davies expects this trend to continue, and talks of a focus on making intuitive experiences players will enjoy.

We've interviewed King alongside each Crush & Tell episode, learning about Saga Adventures, the value of collectible systems, UX, and more.

The six-episode video series has now ended, but Candy Crush VP of marketing Luken Aragon did tease that depending on player response, "there’s every reason to believe we’ll be back for more".

King will be at Pocket Gamer Connects London on January 19th and 20th, joining thousands of industry professionals at the show. Grab your ticket here.