Aonic brings the magic of Sonic to Amiga: Green Hill Zone demo now available

Thirty-five years ago, a question like this could have started an endless argument between friends: could the Amiga have run Sonic the Hedgehog?

As of August 31, 2026, that question finally has something close to a concrete answer. REASSEMBLER has released Aonic: The Green Hill Zone Demo, the first playable version of his ambitious project to bring Sonic the Hedgehog to Amiga. The demo is publicly available on itch.io under a "name your own price" model, and the compressed aonic_demo1.zip file is just 286 kB.

This is not another platform game simply inspired by Sonic, nor a recreation trying to imitate its graphics and speed. Aonic is much more interesting than that: it takes code, data and logic from the original Mega Drive Sonic and adapts them to the very different characteristics of Amiga hardware.

And this is where things get interesting.

A stock Amiga 1200 as the target

REASSEMBLER could have made life much easier by choosing an accelerated Amiga, adding Fast RAM or setting higher hardware requirements. Instead, he decided to do almost exactly the opposite.

The main goal of the project is to understand what could have been achieved on the kind of machine a normal Amiga owner might actually have had during the 1990s. The demo is intended to run on any PAL Amiga equipped with the AGA chipset and 2 MB of Chip RAM, the standard configuration of a stock Amiga 1200.

That choice is deliberate. REASSEMBLER has explained several times that almost anyone still using real Amiga hardware today probably has Fast RAM or some kind of accelerator. Adding either would have made the challenge easier. Aonic instead tries to understand what Commodore's machine, as sold in 1992, could really do.

On paper, the A1200 has a faster processor than the A500 and the AGA chipset, which can handle far more colours. The problem is that many components still compete for access to Chip RAM through a bus that retains several limitations of earlier Amiga architecture. The more complex the graphics become, the more bandwidth they consume, while the CPU, Blitter, Copper and video system all have to share the same resources.

And Sonic is not exactly the kind of game where you can afford to waste frames.

Can AGA keep up with the Mega Drive?

The original Sonic code runs on a Motorola 68000, while the Amiga 1200 uses the more advanced 68EC020. Both CPUs belong to Motorola's 68k family, but that certainly does not make the conversion automatic. Mega Drive and Amiga handle graphics, sprites, scrolling, memory and audio in very different ways.

Aonic also required changes to the tools used to work with Sonic's original data. A modified version of SonicLVL can convert Mega Drive tiles and level data into the format used by the Amiga engine. The foreground uses five bitplanes, giving it a set of 32 colours shared between scenery and sprites, while the background uses 16 colours and linked AGA sprites to create the parallax effect.

Objects on screen present another challenge. On Mega Drive, Sonic himself is normally built from several hardware sprites. On Amiga, many equivalent elements have to be handled through the Blitter, with completely different hardware costs and the need to restore whatever was behind each object after it has been drawn. Otherwise, the BOBs would simply remain printed on the screen.

Over the past few months, the project has therefore become a long series of experiments, profiling sessions and compromises.

Chasing 50 frames per second

The reference point for the entire project is the 50 Hz PAL system. REASSEMBLER developed a profiler capable of measuring Chip RAM bus usage through so-called "colour clocks". The real problem is not so much the average cost of a frame, but the peaks. When the work required exceeds the available budget, the following frame arrives late and the game can drop from 50 to 25 fps. For Sonic, a game built around speed and fluidity, that is far from a minor issue.

One of the most significant optimisations involved Sonic himself. On Mega Drive, the character is built by combining three or four sprites. Aonic initially kept the same structure, but the number of operations required was too high. REASSEMBLER therefore precomposed the character frames, sacrificing around 167 kB of Chip RAM.

The measured result was a 38% improvement in sprite rendering, a 4% reduction in total frame time and, most importantly, 13% fewer dropped frames.

Other solutions make more aggressive use of the Amiga's peculiarities. Static scenery elements such as rocks, spikes and sections of the bridge can be incorporated into the playfield as they enter the visible area, avoiding the need to erase and redraw them continuously.

A revision of the Copper list reduced frame time by 8.4%, while selective use of the mode Amiga developers know as Blitter Nasty reduced dropped frames by another 11% in REASSEMBLER's tests.

These numbers explain the nature of the project rather well. There is no single trick capable of magically turning an A1200 into a Mega Drive. Aonic moves forward by accumulating small and large gains, reducing unnecessary transfers, precalculating data, using Chip RAM where it makes sense and changing some of the architectural choices of the original game whenever they become too expensive on Amiga hardware.

So, can the Amiga actually run Sonic?

That is probably the question most people will ask after watching the demo, and it is also one that should be answered without getting carried away.

REASSEMBLER himself has been very clear. Before release, he stated that the Green Hill Zone Act 1 demo does not yet represent definitive proof. The project is still incomplete, further optimisation remains to be done, and getting one level to run at a certain level of performance does not prove that Sonic the Hedgehog could behave the same way in every possible situation.

And that is probably what makes Aonic more interesting than a simple technical demonstration.

REASSEMBLER is not trying to prove that "the Amiga had nothing to envy from the Mega Drive" or that "Sonic could easily have run on an A1200". He is simply trying to find a way, through optimised code and hardware compromises, to reproduce the speed and graphical splendour of the original game.

In July, he said that he believed it was possible to achieve something very close to the Mega Drive experience while working entirely with Chip RAM. In the same update, he left the door open to an even more extreme, and perhaps even more fascinating, challenge: finding a way to build a version of the engine capable of running on an Amiga 500.

For now, though, we can enjoy this first A1200 version and return to Green Hill Zone.

The demo can be downloaded directly from REASSEMBLER's itch.io page and is still classified as in development. It is the first time the work carried out over the past few months has reached the community in a form more tangible than videos, technical posts and discussions between programmers about how to work around the machine's limits and exploit its strengths.

The beauty of projects like Aonic is that, more than thirty years later, they reignite the old Amiga versus console debate with new arguments. No longer just comparisons based on specifications or old grudges left over from the system wars, but new software actually running on real hardware.

And all of this strengthens an idea that every Amiga fan has argued at one point or another: with deeper knowledge of the hardware and enough development talent, some of the gaps that looked difficult to close at the time might have been considerably smaller than we thought.

The old question therefore remains open, but today we finally have 286 kB containing the kind of answer we always wanted to receive.