From Unity 2018 to Unity 6: Preparing a Physics Puzzler for PC and Mobile

Three months of engine migration, mobile adaptation and store integration for Hugecalf Studios, ahead of a planned October release on the Epic Games Store.

Summary

The challenge: A Unity 2018 physics puzzler on Steam and Nintendo Switch needed new Windows, Android and iOS versions for the Epic Games Store, without changing how it plays.
What we did: Three months of engine migration to Unity 6, touch controls and interface changes, mobile optimisation and Epic Games Store integration, all from one shared repository.
The result: Mobile builds cut from around 500MB to 150MB, 60fps on every phone and tablet we tested, and physics that needed no retuning.

In brief

Overview

Timeline: 2026 (3 months)
Platform: Windows, iOS, Android (Epic Games Store versions, planned)
Genre: Engine Migration
Engagement: Epic Games Store

Built with

Unity
C#
Epic Online Services

Team

When Ski Lifts Go Wrong is Hugecalf Studios' physics-based construction puzzler. Players build ski lifts, bridges and jumps, then see whether their structures carry passengers safely across the mountains. The existing Steam and Nintendo Switch versions were built with Unity 2018. After Epic Games approached Hugecalf about bringing the game to its store, Hugecalf commissioned Ocean View Games to prepare Windows, Android and iOS releases together. Over three months, we migrated the game to Unity 6, a Long Term Support (LTS) release, adapted its controls and interface for mobile, optimised the mobile builds and handled store integration. Quality assurance (QA) was handled separately. The main engineering challenges were deprecated code, ageing packages and software development kits (SDKs), and supporting the different platforms from one shared repository. The legacy Steam integration was retained, but this engagement did not produce a new Steam or Nintendo Switch build. Release on the Epic Games Store is planned for October.

The starting point and completed development work for When Ski Lifts Go Wrong
Area	Before	After development
Engine	Unity 2018	Unity 6 LTS
Release scope	Steam and Nintendo Switch	Epic Games Store on Windows, Android and iOS, planned for October
Mobile input	No mobile version	Tap-and-drop construction and on-screen controls
Mobile build size	Around 500MB before optimisation	150MB
Mobile performance	No mobile version	60fps on the phones and tablets tested
Gameplay consistency	Original Unity 2018 version	Checked through side-by-side play comparisons; no physics retuning required

Updating the Engine and Its Dependencies

Moving from Unity 2018 to Unity 6 meant working through deprecated code and older dependencies as well as upgrading the engine. The new builds use Unity 6000.0.73f1 LTS.

Deprecated Code and APIs

We updated code that relied on deprecated application programming interfaces (APIs) and resolved compatibility issues introduced by the engine migration. The work also included moving the mobile builds to IL2CPP.

Odin Inspector

Odin Inspector needed updating, along with code changes to account for API changes. Updating the package alone was only part of the migration work.

Custom Blood-Splatter Shaders

We fixed compatibility issues in the custom shaders used for the cartoon blood-splatter effects as part of bringing the existing visuals across to Unity 6.

Retaining the Steam Integration

The shared repository retained the legacy Steam SDK integration. The work focused on the new Epic Games Store versions and did not result in a new Steam build.

Supporting Windows, Android and iOS Together

All three Epic Games Store versions were part of the brief from the start. We maintained one shared repository while separating the code needed by each platform.

Platform-Specific Code

We used preprocessor directives and assembly definitions to separate platform-specific code within the shared repository, supporting the different SDKs and build targets.

Epic Games Store Integration

We handled Epic Games Store integration for Windows, Android and iOS, including Epic Online Services. The three releases are planned for October.

Adapting Gameplay for Touch

The desktop controls used the mouse to place and connect structures, with keyboard controls for camera movement, vehicles and shortcuts. We adapted those interactions for phones and tablets, with Adam Kaye leading the gameplay adaptation.

Tap-and-Drop Construction

Building and connecting structures moved to a tap-and-drop model, replacing the desktop click-and-drag interaction.

On-Screen Controls

Keyboard shortcuts became on-screen heads-up display (HUD) buttons, and vehicles received touch controls so players could access those actions without a keyboard.

Touch Targets and Safe Areas

We enlarged interactive elements for finger input and adapted the interface to respect device safe areas.

A Mobile Tutorial in Every Supported Language

We created a mobile-specific tutorial and updated the control terminology across every supported language to describe touch interactions.

Optimising Mobile Builds and Checking Gameplay

The mobile adaptation needed to fit the target devices while preserving the original gameplay. Our development checks included playing the original and ported versions side by side; QA was handled separately.

From Around 500MB to 150MB

Audio and texture optimisation reduced the mobile build to 150MB. This included compressed Wwise sound banks for mobile, texture sizing and texture compression.

60fps on Tested Devices

The mobile builds reached the 60fps target on the Samsung Galaxy A35 5G and Galaxy S25, the iPad Air (2020) and the iPad Pro (M1).

Side-by-Side Gameplay Comparisons

We played the original Unity 2018 version and the new platform builds side by side to check that they played the same. The physics behaviour carried through without retuning.

The Results

Three Months of Development

Completed the Unity 6 migration, mobile adaptation, optimisation and store integration for the planned Epic Games Store releases on Windows, Android and iOS. Release is planned for October.

Original Gameplay Preserved

Side-by-side play comparisons with the original version confirmed gameplay consistency without physics retuning.

150MB and 60fps on Mobile

Reduced the mobile build from around 500MB to 150MB and reached 60fps on the tested Samsung Galaxy A35 5G and Galaxy S25, iPad Air (2020) and iPad Pro (M1).

Gallery

When Ski Lifts Go Wrong gameplay - low-poly snowboarder character outside an alpine log cabin lodge

When Ski Lifts Go Wrong build mode - blueprint construction grid with a structural truss connecting two gondola stations and a planned cable path

When Ski Lifts Go Wrong gameplay - Drag Bridge level fail state with a snowboarder ragdoll thrown against a cliff face

When Ski Lifts Go Wrong gameplay - Round Island level showing twin gondola stations on a floating cliff connected by player-built truss bridges

When Ski Lifts Go Wrong gameplay - The Cannon level showing a low-poly alpine setting with skier ragdoll physics and on-screen control HUD

When Ski Lifts Go Wrong gameplay - The Grand Gondola level showing a large wooden truss tower with gondolas on a cable across a snowy mountain

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Frequently Asked Questions

For When Ski Lifts Go Wrong, we updated deprecated code and APIs, upgraded Odin Inspector and fixed compatibility issues in custom blood-splatter shaders. We also adapted the game for mobile and handled Epic Games Store integration. The work took three months, with QA handled separately.

We played the original Unity 2018 version and the new platform builds side by side to check that they played the same. The physics behaviour carried through without retuning. These were our development checks; QA was handled separately.

Epic Games Store releases on Windows, Android and iOS are planned for October. All three were part of the brief from the start. We retained the legacy Steam integration in the repository, but this engagement did not produce a new Steam or Nintendo Switch build.

We used one shared repository, with preprocessor directives and assembly definitions to separate platform-specific code. The mobile adaptation included tap-and-drop construction, on-screen controls, safe-area support and a mobile tutorial in every supported language.