Project 07 · Game

The Merging Thief

A stealth puzzle game where a thief catches police from behind, absorbs them and grows stronger.

Genre:: Stealth Puzzle, Hyper-Casual
Scope:: Game Design · Level Design · UX/UI · 3D & Materials · Game Feel
Development Time:: 1 Week
Team Size:: 2
Tools:: Unity

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Project Resume

Overview

A hyper-casual stealth puzzle game. A thief sneaks behind police to merge with them, grows stronger and changes color to break through each level and reach the exit.

Platform Mobile (Android)
Team Size 2
Duration 1 Week
Engine Unity

Key Features

Sneak past vision cones and catch police from behind
Merge with police to double your level and change color
Walls, boxes and doors that ask for the right color
Buttons, lasers, keys and locks that build each puzzle
Lockers to hide in while a patrol walks by
Ten top-down levels, each on one vertical screen

My Role

Game Designer & Unity Artist

Owned the game, coordinated the programmer and made everything outside the code, from the ten levels to the art, VFX, UI and ads.

Designed all ten levels, the puzzles and the police routes
Built the 3D, animation, materials, VFX and UI in Unity
Created the Unity pipeline I used for the next year

Design Brief

The publisher liked to make alternative versions of its own hit games and test them with analytics, to see if a new take could repeat the original's success. The Merging Thief was one of them, a hyper-casual puzzle game about a thief and the police, built as a test demo in one week by a programmer and me.

Constraints

A new take on a hitAn alternative version of a game that had already worked for the publisher.
One weekFrom the first level to a playable test demo in one week, with one programmer.
One vertical screenA mobile game in portrait, with the whole level visible from above.
Easy to pick upA hyper-casual game anyone can understand without a tutorial.

Design Goal

I wanted every level to read at a glance from above and still feel hard. Players had to understand, at some point, how they solved a puzzle, and feel the difficulty on the way there. The merge had to sell the fantasy of a thief who absorbs the police and grows stronger with every catch, and the right color had to be the key to every barrier.

From the first catch to the exit door

Sneak in. Merge up. Break out.

SneakSlip past the vision cones of the police.
MergeCatch an officer from behind and grow.
EscapeTake the right color and open the exit.

Player Experience Pillars

Readable puzzlesUnderstood at a glance from above.
Felt difficultyHard enough to feel earned.
A strong fantasyA thief who absorbs the police.
Color is the keyThe right color opens the way.
Juice in every mergeEvery catch is a small show.

Design Solution

Each level is a small top-down maze that fits on one vertical screen, with a door at the start and a door at the end. Police walk set patrols with a vision cone in front, and the thief catches them from behind to merge, doubling in level and taking on a new color. Color walls, boxes, buttons, lasers, keys and lockers turn every merge into a step of the puzzle, and the exit only opens for the strongest color of the level.

Key Design Choices

Catch from behindMerging only works from behind, so every catch is about timing the patrol and reading the vision cone.
Levels that doubleEach merge doubles the thief's level and changes its color, and the thief grows bigger with every catch.
Color opens the wayWalls, boxes, doors and locks ask for the right color, so players pick which officer to catch next.
Higher ranks see moreOfficers of a higher level see farther and sometimes move faster, so the strongest catch is the hardest one.
Hide and waitLockers hide the thief in closed rooms, so players let the patrol pass and catch the officer from behind.

World & Visual Identity

A bank heist in bright, toy-like colors. The levels are blocky and clean, with clear shapes and bank details like protective glass that suggest something precious inside. Police grow bigger, more muscular and warmer in color as they get stronger, so their level reads at a glance.

Visual Principles

Bright and blockyStrong colors and clear shapes made for phones.
A bank to robBank props and protective glass around the loot.
Strength you can seeHats, shades, muscles and size show a cop's level.
Cold to warmPolice colors warm up as their level rises.
The studio's lineA look that fits the studio's line of games.

Results & Learnings

Results

Ten levels in a weekDesigned and built all ten levels in one week with one programmer, from the puzzles and the police routes to the art, the UI and the store assets.
A pipeline that lastedCreated the Unity production pipeline on my first project at 67 Bits, and it became the base of my work at the studio over the next year.
A test that moved onThe test demo reached 2.7K downloads on the studio's Play Store page, and the publisher took the game forward on its own stores.

Learnings

Juice has a nameI already designed visual feedback, but here I learned that games call it juice, and I started designing it on purpose.
Readable, then hardA puzzle has to be understood before it can feel hard, so level design and UX became one job, with the main solution standing out.
Pipeline firstBuilding the pipeline on my first studio project paid off on every game I made at the studio after it.

Media

The work, up close

Project gallery · 1

Gameplay

Roles

Roles & Responsibilities

I owned the game with the studio owner approving the art direction, coordinated the programmer and made everything outside the code.

Design & Coordination

Owned the project and made every game design decision
Coordinated the programmer on the game's systems
Defined the merge, the levels and the color rules
Worked as game designer and Unity artist at the same time

Level Design

Designed all ten levels and every puzzle in them
Placed doors, walls, boxes, buttons, lasers and lockers
Kept the main solution clear among other routes
Made each puzzle readable and still hard to solve

Police & NavMesh

Set up the NavMesh for every police patrol in the game
Set where each officer starts, walks and turns back
Tuned each officer's speed and vision to its level
Placed each patrol to set the timing of every catch

UX & UI

Designed the UX so every level reads at a glance
Added the merge indicator, a circle and arrow under the thief
Designed and built every screen of the game's UI
Kept the whole level visible on one vertical screen

Visual Direction

Led the visual side of the game in the studio's style
Designed the police to show their strength at a glance
Dressed the levels as a bank with protective glass
Built a bright, blocky look with clear shapes for phones

3D, Materials & Light

Modeled the characters, props and levels in 3D for Unity
Tested several shaders and made some of my own for the look
Set the materials and lighting to the approved look
Modeled hats, shades and muscles for stronger police

Animation & VFX

Animated the walk, run, jump and merge of the characters
Made the merge VFX, from puddle to bouncy reveal
Added squash and stretch and objects that fly on impact
Added an alert over the head of officers who spot the thief

Store, Ads & Pipeline

Created the store images and the icons of the game
Made the promotional videos the studio used for ad traffic
Built the Unity pipeline I followed for the next year at 67 Bits
Set the pipeline steps from 3D model to material and light

Full Case Study

The Merging Thief Case Study

Core Loop

Read the level
Avoid the vision cones
Catch from behind
Merge and grow
Open the way

Every level starts with a read. The whole level fits on one vertical screen, so players see the police, their patrols and every barrier before they move. They slip past the vision cones and catch an officer from behind, and the thief absorbs the officer, grows and takes on a new color. That color opens the next part of the level, a wall, a box or a door that would not move before. A level ends one of two ways, at the exit door, which only opens for the strongest color of the level, or with the thief caught by the police, and then it starts over the same way.

Level Design

Feature Introduction

Ten levels, read from above

Purpose

Each level is a small top-down maze on one vertical screen, with a door at the start and a door at the end, built so the whole puzzle reads before the first move.

Design Goal

Show the whole puzzle on one vertical screen before the first move
Make every catch a matter of reading and timing the patrol
Keep the main solution clear while other routes still exist
Make the right color the key that opens every barrier

Key Areas

01 Entrance & Exit DoorsStart, Goal & the Strongest Color
02 Level DoorsMaze Structure & Progress Gates
03 Box WallsColor Gates & Catch Order
04 Push BoxesPush Puzzles & Held Buttons
05 ButtonsSwitches, Traps & Level Control
06 LasersHazards Turned into Tools
07 LockersHiding Spots & Patrol Timing
08 Keys & Locked DoorsSide Goals & Backtracking

Feature Breakdown

Readability & Visual Guidance

Level Start

Show the whole level at once and let players find the goal, the next catch and the way through before moving.

The level starts on one vertical screen seen from above, with nothing hidden. Players see the exit door and its color, the police on their routes and every barrier between them, so the first seconds are a read of the puzzle. The order of the catches is there to be found before the thief takes a step.

Focus

Read, then move.

Find the exit color and the first catch before taking a step.

Visibility

The whole level fits on one screen, so every patrol, barrier and door is in view from the very start.

Color & order

Every barrier shows the color it asks for, so the order of the catches can be read before moving.

Objectives

Primary

Exit Door

The goal of the level, with the strongest color players need to reach before it opens.

Next Objective

Officer

The officer whose color opens the first barrier, the first catch players plan for.

Secondary

Barriers

Walls, boxes and doors that show which colors the level asks for.

Supporting

Lockers

Hiding spots and buttons that help the thief get past the police.

The Police

Show how strong each officer is and what it sees, so players pick their catches and stay out of sight.

Officers grow stronger as their level rises, and their look shows it. Stronger officers wear a hat and dark glasses, carry more muscle and more accessories, and their colors move from cold to warm. Their vision cone shows what they see and reaches farther on stronger ones, so the hardest catch is clear at a glance.

Focus

Read the officer.

Spot the strongest officer, the hardest catch and the key to the exit.

Strength

Hats, dark glasses, muscles and warmer colors show an officer's level before the thief gets close.

Vision

A cone in front of each officer shows what it sees, and the stronger the officer, the farther the cone reaches.

Signals

Level

Lv. Tag

A level tag over every head and a color that runs from blue to red.

Strength

Look

Hats, dark glasses, more muscle and more accessories on stronger officers.

Danger

Cone

The area in front of an officer, where the thief is seen.

Warning

Alert

An alert over an officer's head shows that the thief has been spotted.

Before a Catch

Show the thief when a catch will land, so players line up from behind and stop walking into officers.

A catch only works from behind, and from above it was hard to tell where the thief was facing. A circle under the thief, with an arrow in front, shows when it is lined up, and the cone shows where not to stand. Together they let players read the catch before committing to it, so timing and position decide it.

Focus

Line up, then catch.

Wait for the officer to turn, line up the circle and move in.

Direction

The circle under the thief and the arrow in front show where it is facing and whether the merge will land.

Risk & timing

The vision cone and the patrol route together show the window to slip in behind the officer and make the catch.

Signals

Line-up

Circle

Shown in front of the thief when it is lined up to merge.

Window

Patrol

The moment an officer turns away on its route, which is the time for the thief to move in.

Target

Color

The color the thief takes after the catch, and the barrier it opens.

Reward

Merge

The puddle and the bounce that confirm the catch and show the thief's new color.

Feature Breakdown

Level and Structure

Entrance & Exit Doors

Start, Goal & the Strongest Color

Every level opens with a door at the start and closes with a door at the end, and the goal is always to reach the second one. The exit door is thicker than the doors inside the level and only opens for the strongest color of the level, so the last catch decides the way out and the order of every catch before it.

Role

Sets the goal of every level and the last catch players have to reach

Design Approach

Decisions made

Placed an entrance and an exit door in every level
Made the exit door thicker than the doors inside the level
Gave the exit the strongest color of the level
Kept both doors in view from the first look at the level

Player Impact

Effect on play

Players know the goal of the level from the first look
The exit color tells players which catch comes last
Players plan every catch toward the color of the exit
The thick door reads apart from every other door

Level Doors

Maze Structure & Progress Gates

Thin level doors split each level into parts, like a small maze, and each one bursts open for a thief of its color or a stronger one. I laid out every level so a thief moving forward never outgrows the next door, so each one still needs its own catch and the puzzle stays whole. Going back, a stronger thief opens any door.

Role

Splits each level into a maze that opens one catch at a time

Design Approach

Decisions made

Split each level into parts with thin level doors
Made each door open for its color or a stronger one
Kept the thief from outgrowing the doors ahead of it
Made the doors thin so they read apart from the exit

Player Impact

Effect on play

Players open the level one part at a time
A door's color tells players which officer comes next
Every door ahead still asks for its own catch
Going back, a stronger thief walks through any door

Box Walls

Color Gates & Catch Order

Walls of checkered boxes close parts of the level and break for a thief of their color or any stronger one, bursting into cubes that fly across the room. The thief takes a color by merging with an officer, so every wall points at the officer players need to catch first.

Role

Turns every merge into the key for the next part of the level

Design Approach

Decisions made

Made each wall break for its color or any stronger one
Matched each wall's color to an officer in the level
Placed walls in front of keys and the next part of the level
Sent the broken boxes flying across the room

Player Impact

Effect on play

A wall's color shows which officer to catch
Players plan the order of their catches around the walls
A weaker thief is blocked and needs a new plan
Smashing through a wall feels like a reward

Push Boxes

Push Puzzles & Held Buttons

Some boxes stand in the way and others are there to be pushed onto a button. A colored box only moves for a thief of its color, so a yellow box only moves for a yellow thief. A box left on a button keeps it pressed, so a door stays open or a ray stays on while the thief moves away from it.

Role

Gives players something to move or leave on a button

Design Approach

Decisions made

Made push boxes that clear a path or hold a button
Made colored boxes move only for a thief of their color
Let a box keep a button pressed after the thief leaves
Placed boxes where the path has to be cleared first

Player Impact

Effect on play

Players push a box onto a button to keep it pressed
A box in the way shows which color the thief needs
A held button keeps a ray on while the thief moves away
Players plan where each box ends up before pushing

Buttons

Switches, Traps & Level Control

Buttons are pressed by the thief or held down by a box. Some open closed doors, red ones switch things off, like lasers, and blue ones carry a lightning icon and switch a ray on. The same button can open the way for the thief or trap an officer on its route.

Role

Lets players change the level and turn it against the police

Design Approach

Decisions made

Made buttons that open doors kept closed
Gave red buttons the off switch for lasers
Put a lightning icon on blue buttons that switch rays on
Placed blue buttons near the routes the police walk

Player Impact

Effect on play

The color of a button tells players what it will do
A box on a button frees the thief to move on
Players step on a blue button to trap a passing officer
Players time each press to the officer's patrol

Lasers

Hazards Turned into Tools

Lasers and electric rays cross the level and are switched on and off by buttons. A laser blocks the thief's way until it is switched off. Officers are never killed in this hyper-casual game, and one caught in a ray is paralyzed, so players time the blue button to a passing patrol and walk right past it.

Role

Turns a hazard into a tool the thief uses against the police

Design Approach

Decisions made

Made rays paralyze officers and keep the game light
Placed rays across the paths the patrols walk
Linked every ray to a button the thief can reach
Made lasers block the thief until switched off

Player Impact

Effect on play

Players wait for an officer to step into the ray
A frozen officer lets the thief walk past
Players time the button to the patrol
A laser in the way reads as a puzzle to switch off

Lockers

Hiding Spots & Patrol Timing

Some rooms are closed, with no way to slip around an officer walking toward the thief. For those I put lockers in the level. The thief hides inside, the vision cone passes without seeing it, and once the officer turns away the thief steps out and catches it from behind. Lockers were part of the design from the start.

Role

Gives players a safe way to wait out a patrol in a closed room

Design Approach

Decisions made

Placed lockers in rooms with no way around the patrol
Kept the hidden thief out of every vision cone
Built rooms where waiting is the only way forward
Made lockers part of the design from the start

Player Impact

Effect on play

Players hide and let the officer walk past
The officer turns away, so players step out behind it
Players learn that some rooms ask for patience
A locker in a room tells players to read and wait

Keys & Locked Doors

Side Goals & Backtracking

Some doors carry a padlock that only a key opens, and each lock has a color too. A thief with the key may still need to go back and catch the right officer, while a thief who already has that color walks straight through. Reaching a key can take a catch of its own, to break the wall in front of it.

Role

Adds a side goal that ties a catch to the way out

Design Approach

Decisions made

Gave every lock a color on top of its key
Placed keys behind walls that need a catch to break
Let a thief with the right color open the lock at once
Used keys to send players back through the level

Player Impact

Effect on play

Players read the lock's color before going for the key
Getting a key can take a catch of its own
A wrong color sends players back for another officer
Players plan the key and the lock as one puzzle

Impact

How a level shapes each move

Read First

The whole level fits on one vertical screen, so players read the patrols, the barriers and the exit color first, and plan the order of their catches before the thief takes a single step.
Time the Patrol

Officers walk set routes at set speeds, so players learn each route, wait for an officer to turn away and slip in behind it. Every catch is a question of timing and position.
Choose the Order

Every barrier shows the color it asks for, so players decide which officer to catch next and which to leave for later. A catch in the wrong order means going back for another officer.
Hide and Wait

Closed rooms leave no way around an officer walking toward the thief, so players hide in a locker, let the patrol walk past and step out behind it to make the catch.
Use the Level

Boxes hold buttons down and rays freeze officers, so players change the level to clear their path, stepping on a blue button at the right moment to stop a patrol and walk past.
Find the Way

Some puzzles have more than one way through and the main one stands out, so players always find a solution and still feel that they worked out the puzzle on their own.

Police & Merge

Feature Introduction

Catch from behind, merge, grow

[object Object],[object Object],[object Object]

Design Principles

Sell the fantasy of a thief who absorbs the police, with every catch making it visibly bigger, stronger and a new color
Make catching from behind the one rule of the merge, so every catch is a question of reading a patrol and choosing the moment to move in
Show an officer's strength before the catch through color, size and accessories, so players judge each catch at a glance on a small screen
Tie every merge to the level, with each new color opening a barrier, so the order of the catches becomes the puzzle itself

Feature Breakdown

The police, in detail

Patrol Route

NavMesh · Set start · Set reach · Set speed

Every officer walks a route I set on the NavMesh, from where it starts to how far it goes and how fast it walks. The route repeats, so it can be learned, and its turns open the moments when the officer's back faces the thief. Speed and route together set the window for every catch.

Role

Sets the timing of every catch in the level

Behavior

How it acts in the level

Walks a route set on the NavMesh
Starts and turns at set points
Walks at a speed set per officer
Repeats the same route every time

Counterplay

How players get past it

Learn the route by watching it
Wait for the officer to turn
Slip in behind it and catch
Freeze it with a ray on its path

Design Intent

Why it was designed this way

Make every catch a timing puzzle
Give each catch a fair window
Keep patrols easy to learn
Let the level shape every route

Vision Cone

Front only · Range by level · Alert

Each officer sees through a cone in front of it, so players always know where not to stand. Stronger officers see farther, so their cone covers more of the level. When an officer spots the thief, an alert appears over its head. Lockers hide the thief from the cone, and an officer's back is where every catch begins.

Role

Shows players where they can and cannot stand

Behavior

How it acts in the level

Sees only in a cone in front
Sees farther at a higher level
Shows an alert when it spots
Cannot see into a locker

Counterplay

How players get past it

Stay out of the cone
Come in from behind
Hide in a locker and wait
Mind the range of strong officers

Design Intent

Why it was designed this way

Make danger visible at a glance
Keep every officer's back open
Give closed rooms a way through
Make strong officers harder to reach

Officer Strength

Cold to warm · Hats · Shades · Muscles

Officers grow stronger as their level rises, and I modeled the change so it reads at once. Stronger officers wear a hat and dark glasses, carry more muscle and more accessories, and their colors move from cold to warm. They also see farther and some move faster, so the strongest officer is the hardest catch.

Role

Shows the level of every officer before the catch

Behavior

How it acts in the level

Colors warm up as levels rise
Hats and dark glasses on top
More muscle, more accessories
Sees farther, sometimes faster

Counterplay

How players get past it

Read each level at a glance
Find the officer the exit needs
Plan the catches by strength
Take care near strong officers

Design Intent

Why it was designed this way

Make strength readable on a phone
Show progress through color
Make the hardest catch obvious
Fit the bright, blocky look

Feature Breakdown

The merge, in detail

Merge

Catch from Behind, Double Up, Change Color

The merge is the one action of the game. When the thief reaches an officer of its own level from behind, both become one body, the thief's level doubles and it takes on the color of its new level. One and one make two, two and two make four, then eight. The new color is what opens the next wall, box, door or lock.

Role

Turns every catch into growth and a key to the level

Design Approach

Decisions made

Allowed the merge only when the thief reaches an officer from behind
Doubled the thief's level with every merge, from 1 to 2, 4 and 8
Gave every level its own color, the key to the next barrier
Made the thief grow bigger with each merge it lands

Player Impact

Effect on play

Players circle each officer and wait for the right moment
Every catch changes what the thief can open next
Players watch the thief grow and feel it getting stronger
The circle and arrow under the thief show when a merge will land

Game Feel

Feature Introduction

A merge you can feel

[object Object],[object Object],[object Object]

Design Principles

Make every merge a big, clear moment that sells the fantasy of a thief absorbing the police, exaggerated enough to read on a phone
Give each catch a visible change, with the thief growing bigger and taking a new color as it bounces out of the puddle
Use squash and stretch on the characters so every walk, run, jump and merge has weight and stays readable from above
Make collisions loud, with boxes and objects flying far across the level when the thief runs into them

Design Iterations

01 Merge Indicator

Problem

Players ran into officers from the front

Players often walked into an officer face first or reached it at an angle, and the catch failed. From above it was hard to tell whether the thief was lined up to merge or about to be seen.

Cause

Nothing showed if the merge would land

The game gave no sign of the direction the thief faced or of whether the catch would work, so players found out only when it failed.

Solution

Added a circle and an arrow to the thief

A circle under the thief, with an arrow in front, shows when it is lined up to merge, so players see the catch first and stop running into officers face first.

Drew a circle under the thief
Added an arrow for the way it faces
Kept it on the ground, under the action

Result

Players lined up the catch before moving

Players stopped running into officers face first and started lining up every catch, so the merge became a matter of timing and positioning, the way the puzzle intended.

Fewer catches from the front
Players lined up before moving
Timing became the challenge

02 Patrol Timing

Problem

Some patrols made a level unfair or dull

A level is only fun when the timing works. An officer walking too fast on its route left no time to catch it from behind, and a route that was off broke the puzzle the level was built around.

Cause

Speed and route set the window to catch

The window to catch an officer comes from how fast it walks and where its route turns, so a small change in either one changed the whole level.

Solution

Tuned routes, speeds and the level itself

Played every level, tuned each officer's route and speed on the NavMesh and moved parts of the level until each catch had a fair window.

Tuned each officer's speed
Reworked routes on the NavMesh
Moved parts of the level when needed

Result

Every catch got a fair window

Each level kept a clear moment to slip behind the officer it needed, so the challenge came from reading the patrol and the order of the catches.

A fair window for every catch
Puzzles that read and still felt hard
Patrols players could learn

03 Materials & Shaders

Problem

The look had to match the studio's line

The game needed a look that matched the studio's profile and the line of games it was making at the time, all with a similar visual style, and it had to be approved by the owner, who was also the art director.

Cause

Each shader changed the colors and the light

Every shader I tried gave the colors and the lighting a different result, so reaching the approved look took more than picking one.

Solution

Tested shaders, then tuned materials and light

Tested several shaders, made some of my own and tried others used in earlier projects, then set the materials and the lighting until the game looked the way the approved art direction asked.

Tested several shaders
Made some shaders of my own
Tuned the materials and lighting

Result

Reached the approved look

The game got a bright, blocky look with clear shapes that fit the studio's line of games, approved by the art director.

Approved by the art director
Fit the studio's line of games
Clear shapes in strong colors

Development

Pipeline, Models & Materials

Conclusion

Design Conclusions

The Merging Thief was my first game as a Unity artist at 67 Bits and my first fixed job in the industry. In one week, with one programmer, I owned the game from the ten levels to the art, and the pipeline I built for it became the base of my work at the studio for the next year.

It also gave me a name for something I already did. My design degree had taught me visual feedback, and here I learned that games call it juice, and started designing it on purpose. The other lesson came from the levels, where readable and hard had to live in the same puzzle.

Design Takeaways

Feedback became a design tool

My design degree taught me visual feedback, and here I learned that games call it juice. Knowing the name made me design it on purpose, starting with the merge.
Readable comes before hard

A puzzle has to be understood before it can feel hard. Level design and UX became one job here, with the main solution standing out and players able to see how they solved it.
A pipeline worth repeating

Building the pipeline on my first studio project paid off on every game I made at 67 Bits after it, since the next year of work followed the steps I set up for this one.

Next project

Flip Phone