The Logic Behind Match-3 Games: How Unity and C# Make the Magic Work

At some point in our lives, we all have played a match-3 game. Candy Crush alone has 3.6 billion downloads, so… yeah, we probably all have! Ever since Bejeweled was published back in 2001, this genre of games has cemented itself as a synonym of mobile games and has captured our attention even to this day. With notable recent examples being Royal Match and Game of Thrones Legends, these games are still going strong more than 20 years later!

But how many of us actually know how these games work?

Turns out, you can pretty much create your very own Match-3 game with Unity and C#. Of course, you'll need some nice assets, sound effects, and animations for the fancy stuff, but at the core, Unity can get you set up to take care of the basics pretty much right away.

The Technical Foundation

Match-3 games use a 2D grid data structure—basically a spreadsheet where each cell holds information about what tile is there. In Unity, this is typically implemented as a Grid2D<T> struct that wraps a single-dimensional array internally (since C# stores 2D arrays as jagged arrays, a flat array with index math is actually more efficient). The struct keeps track of the grid's width and height, then uses the formula array[x + y * width] to convert 2D coordinates into a 1D array position.

This is where the magic starts. Your game board is a matrix of data that the game logic manipulates independently from what you see on screen. Each cell in your array stores a tile type (an enum or integer representing gems, candies, whatever), a state flag (normal, matched, falling), and possibly a reference to the visual GameObject.

Here's the important part: the game exists in two parallel worlds. There's the logic world (pure data in arrays) and the visual world (the pretty sprites players see). When you swap two gems, you're actually swapping data in an array first—literally just tiles[pos1] = tiles[pos2] and vice versa—then the visual animation happens to match. This separation keeps everything clean and organized, and it means you can test your game logic without even opening Unity's scene view.

The Core Game Loop

Let's take a quick look at some of the logic needed to make things work:

1. Swap Detection

Your basic movement detection—the player makes a move and it registers. The game uses input detection (either OnMouseDown() for mouse or Unity's Input System for touch) to catch when you click or tap a tile, then checks if the two tiles you're trying to swap are actually next to each other. The adjacency check is simple math: if (Mathf.Abs(tile1.x - tile2.x) + Mathf.Abs(tile1.y - tile2.y) == 1) confirms they're neighbors (no diagonal swaps in classic match-3!).

Here's what happens behind the scenes: The swap happens in the 2D array first—you're exchanging positions in data, not moving pictures around. The code stores both tile types in temporary variables, swaps them in the array, then checks if this swap creates a match. If it does, great! The animation plays. If not, you swap them back and play a little "invalid move" wiggle animation.

Only after the logic confirms it's a valid swap do the visual sprites animate smoothly to their new positions using either Unity's Animation system or DOTween for more control. The animation duration is typically 0.25 seconds—fast enough to feel responsive, slow enough to be visually clear.

2. Match Detection

It doesn't stop at movement—the game must look for matches generated by each player's move. Here's a cool fact: for a standard 8x8 grid, there are only 96 possible spots where a match-3 could exist (6 positions per row/column × 16 lines). That's it! So checking the whole board is actually super fast—we're talking milliseconds.

The algorithm works like this: After each swap, the game scans horizontally and vertically from each tile. You can do this in two ways:

Method 1: The simple scan - Start at position (0,0), move right counting consecutive matching tiles. When you hit three or more, add them to a List<Match> for removal. Do this for every row, then repeat vertically for columns.

Method 2: The smart scan - Only check the tiles adjacent to the ones that just moved. Why scan the whole board when only two tiles have changed? This is more efficient but requires careful edge-case handling.

Either way, you're using nested loops and comparison operators. When it finds three or more, boom—those tiles get marked for removal in a match collection. The actual removal happens in a batch after all matches are found (never remove during the scan, or your indices get messed up).

3. Cascading Combos

This is the magic right here, and it's not happening just once or twice—it cascades! The player makes a match, the system registers that, more tiles fall into place creating another match, which in turn… you get the idea!

So how does it actually work? The game runs a continuous loop that doesn't stop until the board settles down. Here's the technical flow:

1. Match detected → tiles marked in the array (set state to "matched")
2. Remove phase → matched tiles deleted, leaving null/empty spaces
3. Gravity phase → Starting from the bottom row, move tiles down into empty spaces using a fall algorithm
4. Spawn phase → Fill empty top row positions with new random tiles
5. Re-check phase → Call FindMatches() again on the entire board
6. Decision point: Found more matches? Back to step 1. No matches? Exit loop, return control to player

This is implemented as either a while(matchesFound) loop or a recursive function that calls itself. The key is the re-check in step 5—that single line of code creates the entire cascading magic. Your game state machine needs a "processing" flag to prevent player input during this cascade sequence.

4. Special Tile Recognition

As we all know, not all tiles are created equal. This is where you add that special flavor of strategy and gratification—perhaps a tile that eliminates all tiles of a color, or brings a big explosion that takes half the screen, or a simple score multiplier. The floor is yours to be creative in your choices when it comes to special tiles.

But here's what's happening under the hood: The algorithm doesn't just count matches, it looks at their shape and size. When FindMatches() runs, it's not just returning a count—it's returning a MatchInfo object that contains:

• The matched tiles' positions
• The match type (horizontal, vertical, L-shape, T-shape)
• The match length (3, 4, 5, or more)

Your code then evaluates: "Okay, this is a 4-tile horizontal match, so spawn a horizontal rocket at the middle position." An L-shaped or T-shaped match? That's detected by checking if a tile participates in both a horizontal AND vertical match simultaneously—set theory, basically. That intersection point becomes your special tile spawn location.

The power-up logic looks something like:

• 4 tiles in a line → Rocket (clears entire row/column)
• 5 tiles in a line → Color bomb (clears all tiles of one color)
• L or T shape → Bomb (3x3 area clear)
• 2 power-ups matched → Combined super effect (custom behavior)

The detection happens during the match verification phase—the code analyzes the geometry of what you matched and decides what power-up you deserve based on a lookup table or switch statement.

Controlled Chaos: The RNG Problem

Now, we all know there's a certain degree of randomness to this kind of game, specifically in tile generation and placement. But this aspect cannot be surrendered to chance—there's got to be controlled chaos to make the game playable.

Pure randomness? That's a disaster waiting to happen. Using Random.Range(0, numberOfTileTypes) for every single spawn creates two major problems:

1. Dead boards - No possible moves exist
2. Cascading disasters - Too many automatic matches, player does nothing and wins

The solution is weighted randomness implemented through probability tables. Instead of each tile having equal chance, you maintain an array of spawn weights that adjust dynamically:

float[] spawnWeights = {0.20, 0.20, 0.20, 0.20, 0.15, 0.05}; // 6 tile types

The rarest tiles get lower weights. You then use a weighted random selection algorithm (pick a random float between 0-1, iterate through accumulated weights until you exceed that value). But here's the smart part—these weights change based on:

• Current board state - If red tiles are abundant, decrease red spawn weight
• Level difficulty - Early levels have higher weights for common colors (easier matches)
• Recent player performance - Struggling? Slightly increase spawn weights for colors already on the board
• Power-ups present - Don't spawn 3 bombs in a row, spread them out

The algorithm should always check for impossible states (boards where no matches are possible) before handing control back. This "possible moves" checker scans every tile and simulates swaps with its neighbors, looking for at least one that would create a match. If none exist, the game either reshuffles the board or spawns a helpful tile. This runs after every cascade completes—usually takes 1-2 milliseconds on modern hardware.

The spawn algorithm should also be kind with the player, not handing them the winning swap on a silver platter, but gently pushing them in the right direction, with the amount of "push" changing during the player's journey. This is sometimes called "rubber-banding" in game design—the game subtly helps struggling players and challenges dominant ones.

The Two-World System

One critical thing that makes match-3 games work smoothly: separating logic from visuals through what's called the Model-View separation pattern.

What this means in practice:

• Game logic (the Model) = Match3Game.cs managing tile states in arrays, match detection algorithms, and scoring calculations (the brain)
• Visualization (the View) = Match3Skin.cs that reads game state every frame and updates SpriteRenderers, positions, and animations (the body)
• Communication = The Model fires events like OnMatchFound or OnTilesSwapped, the View listens and responds with animations

State transitions are animated with smooth timings (usually around 0.25 seconds for swaps, 0.15 seconds for tile destruction, 0.2 seconds for falling), but the logic doesn't care about that—it's already calculated the next state. The View is always playing catch-up, displaying what the Model decided 200 milliseconds ago.

This might seem like extra work, but it's actually genius. Want to change how the game looks? No problem—just swap out the visual script, the Model doesn't change. Want to tweak the rules? Touch the logic script, visuals stay the same. Want to add a "replay" feature? The Model already stored every state change; just play them back through the View. Clean separation = happy developers and easier debugging.

You can even run automated tests on your Model without Unity being open—pure C# unit tests that verify match detection, cascading logic, and randomness balance. No graphics required.

The Animation Pipeline

One often-overlooked technical piece: animation sequencing. When tiles match, multiple things happen simultaneously:

1. Match particles spawn at tile positions (0.0s)
2. Tiles scale down slightly (0.0-0.1s, ease-in)
3. Tiles fade out (0.05-0.15s)
4. Score popup appears (0.1s)
5. Tiles above start falling (0.2s)
6. New tiles spawn and fall (0.3s)
7. Next match check (0.5s)

These timings are carefully choreographed so each animation completes before the next system needs that tile's position. If your tile-falling animation is 0.2 seconds but your match-check happens at 0.15 seconds, you'll detect false matches on tiles that haven't reached their destination yet.

Unity's Coroutines handle this sequencing, or you can use DOTween sequences that chain animations with callbacks. The important thing is keeping your animation durations in sync with your game logic timing.

The best part of it all? You can create a fully functional match-3 game with just Unity (free), Visual Studio (free), C# knowledge, and basic 2D assets. The core logic—the grid implementation, the matching algorithm using nested loops, the cascading system with recursive checks—can be built in a weekend by someone with intermediate C# skills (you should understand arrays, loops, and basic data structures). Everything else is polish, but that foundation? That's pure logic!