What is a game engine: Yevhen Kasyanenko’s opinion and perspective

“To put it simply, without an engine, everything would fall apart. We put the pieces together, and the engine holds them together and keeps the game world from falling apart,” explains Yevhen Kasyanenko, a leading expert at KISS Software.

In this article, Yevhen and I explain how game engines have changed the approach to game development and which technologies are shaping the future of the industry today.

The main functions of a game engine

Before delving into the details, let’s remember that a game engine is a software foundation that takes on routine work and gives authors time for ideas. Even a simple version opens the way to the market if its capabilities match the task.

Graphics rendering – creating 2D and 3D images in real time

Modern engines can create realistic and stylized visual effects:

• trace rays, creating natural light even on a low-end laptop;
• apply shaders that stylize the image to look like a cartoon or 80s neon;
• work with PBR materials to make metal shine and fabric look soft.

“Today, we add daylight and night light with a single slider—it used to take weeks,” notes Yevhen Kasyanenko.

Physical module – the laws that players believe in

The physical engine is responsible for the realistic behavior of objects in the game world. It simulates all sorts of things:

• Gravity – so that objects don’t hang in the air, but fall, bounce, and fly apart as they should.
• Collisions – so that the hero does not pass through walls, and the ball bounces off the floor according to all the laws of the genre.
• Destructibility of objects – when walls break, glass shatters, and a wooden fence flies apart into splinters after being hit by a grenade launcher.
• Liquids and fabrics – water splashes, smoke swirls, and the hero’s cloak flutters beautifully in the wind, rather than just sticking to his back.

“A good physics engine is like a stunt coordinator in a movie: it makes everything look spectacular, but at the same time, it doesn’t break after the first jump. The industry often uses powerful engines like Havok, PhysX, or Bullet, which are behind many of the cool effects that we take for granted,” adds our expert.

So the next time a brick falls on your head in a game, know that it’s not a bug, it’s physics at work.

Artificial intelligence

NPCs are characters controlled by a computer, not a human. Today, their behavior is far from just pre-programmed routes. Artificial intelligence helps them react naturally and adapt to the actions of a live player.

The AI-based engine for non-player character behavior is responsible for the following:

• Smart routes and reactions. Characters calculate the shortest path, avoid obstacles, seek cover, and change tactics if you attack too aggressively. As a result, each encounter feels fresh, rather than scripted.
• Adaptive difficulty. The AI analyzes the frequency of your misses or successful hits and subtly adjusts the balance. Beginners will have more time to react, while experienced gamers will face faster and more accurate opponents. This approach keeps a wide audience engaged.
• Realistic animation. In Hellblade II, the developers trained a neural network to recognize the actress’s emotions and immediately transfer them to the heroine’s model. The character’s face moves naturally, and the studio saves hours of animator work.
• Lively dialogues. Advanced games use language processing models so that NPCs can construct responses from dozens of options instead of repeating the same phrase.
• Automatic content generation. AI is capable of creating side quests, allocating resources, and coming up with short lines on the fly, reducing the cost of manual development.

“High-quality AI makes the game world convincing and reduces content costs for the studio. We often combine two approaches: clearly defined rules for stability and machine learning when we need to adapt to complex situations,” notes Yevhen Kasyanenko.

Audio system – music that guides

Good sound doesn’t just fill the silence, it hints at what’s going on around you. When you approach a waterfall, the sound of water gradually increases, and in a foggy forest, your footsteps become slightly muffled, an arrow whistles from the left—and you know exactly where the danger is coming from.

To achieve this level of accuracy, sound engineers use FMOD or Wwise engine plugins. These allow them to:

• place sound sources in 3D space—the player hears the direction and distance;
• change the timbre and volume in real time—the music gets louder during combat and quieter during cutscenes;
• add environmental effects—underwater, the sound is slightly “muffled,” and in a stone corridor, there is an echo.

“Let’s say the player is running from a cave to the market square. The game engine allows you to mute the echo of the tunnel in a fraction of a second, mix in city noise, and smoothly bring in the battle soundtrack when the fight with enemies begins. Everything happens without loading screens and without a noticeable drop in FPS,” says Yevhen Kasyanenko.

Cross-platform compatibility – one code, many screens

Today, players expect a project to run anywhere – on a PC, console, tablet, or phone. Unity, Unreal Engine, and Godot engines can compile the same source code for different devices in almost one click.

How this helps business:

• Time savings. There is no need to write separate versions; teams edit the common repository in parallel.
• Simultaneous release. Users get the game immediately on all platforms, and marketing works more effectively.
• Fast patching. Updates or bug fixes are rolled out for all platforms in a day, not a week.

“At KISS Software, we recently ran a multi-platform puzzle platformer. Thanks to shared configurations and an automatic build server, the release on iOS and Android came out six weeks ahead of schedule—without any unnecessary rework. This is how a simple game engine turns into a multi-platform factory with one build server, one QA plan, and a single version of data. The team saves up to 30% of the budget because it doesn’t maintain three separate departments for PC, console, and mobile,” says our specialist.

The basics of creating game projects

Game development is a chain of understandable steps. Let’s break down the process so you can see where creativity is needed and where cold calculation is needed.

Key stages

1. Concept. We determine the genre (shooter, RPG, strategy, arcade, etc.), mechanics—player interaction with the world, level system, combat system—and audience. It is important to understand who the game is being created for: casual players, hardcore gamers, or a specific age group.
2. Choosing an engine. At this stage, it is important to understand which tool is right for the task: whether it will be a compact prototype or a graphically rich project. Unity is great for indie and mobile games—it is versatile and flexible. If you need photorealism and high detail, Unreal Engine is the most popular choice. And for experiments, small teams, and prototyping, the lightweight and free Godot is convenient. It all depends on what you are doing and what resources your team has.
3. Content creation. 3D models (made using Blender, 3ds Max, Maya), 2D sprites (Photoshop, Aseprite, Krita), animations (Spine, DragonBones, built-in animation tools of engines).
4. Programming. This is when everything in the game starts to work: enemies think, multiplayer connects, and the interface appears on the screen. The code determines how the hero reacts to your actions, how stable the game is, and how easy it is to refine it later. Different engines use different languages. For example, Unity often uses simple and convenient C#, Unreal Engine uses powerful C++, and Godot prefers lightweight Python, which is great for quick prototypes and small projects.
5. Testing. We catch bugs, balance the economy, and run load tests. Depending on the platform and tasks, we use different tools. For example, Visual Studio Debugger helps find errors in the code, TestFlight helps test mobile games on iOS, and Steamworks SDK is useful for integrating and testing games in the Steam ecosystem.
6. Optimization and release. In the final stage, we bring the game to a stable 60 FPS — we optimize performance so that it runs smoothly on all devices. After thorough testing, we send the finished build to Steam, the App Store, Google Play, and console stores to make your game as widely available as possible.

“An indie team approached us with a prototype of a survival game. They used Godot, but encountered eternal night in their virtual world – the lighting shines and the shadows fall apart. We migrated their scenes to Unity URP, configured the shader graph, and added a dynamic day-night cycle. As a result, not only did the FPS increase by almost one and a half times, but the visuals were also significantly transformed, and players on Discord even wrote that the build looks like a completely new game,” recalls Yevhen Kasyanenko.

The future of game engines: new technologies

Technology is growing faster than patches can be downloaded. Here are the key trends that will shape tomorrow’s answer to the question of what a game engine is:

• Ray Tracing 2.0. Previously, light in games was “painted” — shadows and reflections did not look very natural. Now, ray tracing technology makes light behave like it does in real life: sunbeams reflect off water, shadows change depending on the time of day, and objects seem to come to life. And the coolest thing is that such realistic images are now even available on phones! Unreal Engine has added another feature – Lumen, which helps light change right during gameplay, making everything even more natural.
• Machine learning. Characters in games should move smoothly and naturally. Previously, this was done by recording the movements of real people in special studios. This is expensive and time-consuming. Now, with the help of artificial intelligence, games themselves “learn” to create animations by selecting movements for the character’s skeleton. This reduces costs and speeds up the process, and developers can spend the money they save on something else cool.
• VR and AR. Virtual and augmented reality is when you put on glasses and enter another world or see digital objects right in front of you. Unity has learned to quickly launch games on the new Apple Vision Pro headset in literally seconds. This means you wait less and get into the game faster.
• Cloud Gaming. If you have a weak computer or just want to play without installing anything, cloud gaming is the way to go. The game runs on powerful servers on the internet, and you see and control it through streaming video. To keep everything running smoothly, the engines learn to “keep a reserve” of frames, that is, to adjust to the speed of the internet and not slow down, even if the connection is unstable. This means you can play anywhere and on any device.

“Tomorrow, your game could be running on your refrigerator screen. Prepare your engine for any screen size,” jokes our expert.

Why is it important to develop games with professionals?

Each of the above areas is a separate profession. One mistake in collision settings and the character falls below the level. At KISS Software, we take responsibility to ensure that this does not happen. We provide a full cycle of game development:

• Engine selection. We analyze the idea, budget, and deadlines. We offer Unity for cross-platform or Unreal for cinematography.
• Game design. We reduce the GDD document to the first level, which “hooks” in 30 seconds.
• Testing and optimization. We close the bug report while it’s still in Jira, not on Reddit.
• Post-release support. We release patches, seasonal events, and turn DLC into a new source of revenue.

When you work with KISS Software, you get a team of real pros who are ready to make a game of any complexity—from a simple mobile game to a large-scale 3D action game on the most modern engines.

Conclusion

Game engines are constantly evolving, surprising us with new features that seemed like science fiction just yesterday. Choosing the right engine means making the team’s work easier and the game stable and enjoyable for players.