<s>
The	O
Retro	B-Application
Engine	I-Application
is	O
a	O
multiplatform	B-Operating_System
game	O
engine	O
developed	O
by	O
Australian	O
programmer	O
Christian	O
Whitehead	O
,	O
best	O
known	O
for	O
its	O
use	O
in	O
Sega	O
's	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
series	I-Application
.	O
</s>
<s>
Unlike	O
most	O
modern	O
game	O
engines	O
,	O
the	O
Retro	B-Application
Engine	I-Application
is	O
primarily	O
tailored	O
for	O
creating	O
two-dimensional	O
games	O
like	O
those	O
released	O
for	O
32-bit	O
or	O
below-era	O
consoles	O
,	O
such	O
as	O
the	O
Sega	B-Device
Saturn	I-Device
,	O
Sega	B-Operating_System
Genesis	I-Operating_System
or	O
the	O
Super	B-Application
Nintendo	I-Application
Entertainment	I-Application
System	I-Application
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
the	O
engine	O
focuses	O
more	O
on	O
raster	B-Algorithm
graphics	I-Algorithm
and	O
palette	B-Data_Structure
manipulation	I-Data_Structure
,	O
although	O
it	O
does	O
feature	O
support	O
for	O
widescreen	O
graphics	O
and	O
online	O
functionality	O
.	O
</s>
<s>
Australian	O
programmer	O
Christian	O
Whitehead	O
created	O
the	O
Retro	B-Application
Engine	I-Application
for	O
use	O
with	O
a	O
2007	O
fangame	B-Application
entitled	O
Retro	O
Sonic	B-Application
,	O
which	O
is	O
based	O
upon	O
the	O
original	O
Sonic	B-Application
games	O
released	O
for	O
the	O
Sega	B-Operating_System
Genesis	I-Operating_System
.	O
</s>
<s>
The	O
game	O
became	O
notable	O
after	O
its	O
release	O
for	O
its	O
accuracy	O
to	O
the	O
games	O
,	O
despite	O
not	O
being	O
a	O
ROM	O
hack	O
or	O
modification	O
to	O
an	O
existing	O
Sonic	B-Application
game	O
.	O
</s>
<s>
Retro	O
Sonic	B-Application
later	O
merged	O
with	O
two	O
other	O
Sonic	B-Application
fangames	B-Application
,	O
Sonic	B-Application
XG	O
and	O
Sonic	B-Application
Nexus	O
,	O
to	O
form	O
Retro	O
Sonic	B-Application
Nexus	O
.	O
</s>
<s>
In	O
2009	O
,	O
Sega	O
asked	O
fans	O
for	O
ideas	O
on	O
a	O
game	O
to	O
port	O
to	O
iOS	B-Application
.	O
</s>
<s>
As	O
a	O
response	O
,	O
Whitehead	O
produced	O
a	O
proof-of-concept	O
video	O
showing	O
Sega	O
's	O
1993	O
Sega	B-Device
CD	I-Device
game	O
Sonic	B-Application
CD	I-Application
running	O
on	O
an	O
iPhone	B-Device
.	O
</s>
<s>
Sega	O
later	O
officially	O
released	O
the	O
port	O
in	O
2011	O
for	O
various	O
platforms	O
,	O
such	O
as	O
the	B-Operating_System
Xbox	I-Operating_System
360	I-Operating_System
,	O
PlayStation	B-Operating_System
3	I-Operating_System
,	O
Windows	O
,	O
iOS	B-Application
and	O
Android	B-Application
.	O
</s>
<s>
Whitehead	O
,	O
along	O
with	O
fellow	O
Sonic	B-Application
scene	O
member	O
Simon	O
"	O
Stealth	O
"	O
Thomley	O
,	O
were	O
later	O
commissioned	O
to	O
create	O
remakes	O
of	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
and	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
2	I-Application
using	O
the	O
engine	O
,	O
released	O
for	O
mobile	O
platforms	O
in	O
2013	O
.	O
</s>
<s>
In	O
2014	O
,	O
to	O
celebrate	O
the	O
twentieth	O
anniversary	O
of	O
the	O
release	O
of	O
Sonic	B-Application
3	O
&	O
Knuckles	O
,	O
Whitehead	O
and	O
Thomley	O
produced	O
a	O
proof-of-concept	O
showing	O
the	O
game	O
using	O
the	O
engine	O
on	O
an	O
iPhone	B-Device
.	O
</s>
<s>
In	O
2015	O
,	O
Whitehead	O
,	O
Thomley	O
's	O
studio	O
Headcannon	B-Application
,	O
and	O
PagodaWest	B-Application
Games	I-Application
collaborated	O
on	O
an	O
original	O
Sonic	B-Application
game	O
using	O
the	O
Retro	B-Application
Engine	I-Application
titled	O
Sonic	B-Application
Mania	I-Application
,	O
which	O
released	O
August	O
2017	O
,	O
with	O
DLC	O
titled	O
Sonic	B-Application
Mania	I-Application
Plus	O
being	O
released	O
in	O
July	O
2018	O
.	O
</s>
<s>
In	O
2019	O
,	O
Whitehead	O
,	O
in	O
collaboration	O
with	O
other	O
members	O
behind	O
Sonic	B-Application
Mania	I-Application
,	O
founded	O
a	O
new	O
video	O
game	O
studio	O
named	O
Evening	O
Star	O
.	O
</s>
<s>
In	O
reference	O
to	O
the	O
studio	O
name	O
,	O
the	O
Retro	B-Application
Engine	I-Application
initially	O
had	O
been	O
renamed	O
the	O
Star	B-Application
Engine	I-Application
.	O
</s>
<s>
In	O
October	O
2021	O
,	O
Evening	O
Star	O
announced	O
development	O
was	O
underway	O
for	O
a	O
game	O
using	O
the	O
Star	B-Application
Engine	I-Application
.	O
</s>
<s>
In	O
conjunction	O
with	O
this	O
,	O
it	O
was	O
announced	O
that	O
the	O
Star	B-Application
Engine	I-Application
had	O
been	O
turned	O
into	O
a	O
separate	O
engine	O
with	O
a	O
focus	O
on	O
3D	O
rendering	O
,	O
with	O
the	O
Retro	B-Application
Engine	I-Application
remaining	O
as	O
their	O
2D	O
game	O
engine	O
.	O
</s>
<s>
In	O
January	O
2021	O
,	O
an	O
open-source	B-License
decompilation	O
of	O
the	O
Retro	B-Application
Engine	I-Application
versions	O
of	O
Sonic	B-Application
CD	I-Application
,	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
,	O
and	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
2	I-Application
were	O
released	O
,	O
allowing	O
the	O
latter	O
two	O
games	O
to	O
be	O
run	O
natively	O
on	O
PC	O
platforms	O
.	O
</s>
<s>
The	O
Retro	B-Application
Engine	I-Application
was	O
also	O
used	O
for	O
the	O
compilation	O
Sonic	B-Device
Origins	I-Device
in	O
2022	O
,	O
which	O
includes	O
remakes	O
of	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
,	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
2	I-Application
,	O
Sonic	B-Application
CD	I-Application
,	O
and	O
Sonic	B-Application
3	O
&	O
Knuckles	O
.	O
</s>
<s>
Reviewers	O
praised	O
the	O
Retro	B-Application
Engine	I-Application
for	O
its	O
performance	O
,	O
which	O
has	O
been	O
called	O
superior	O
to	O
simply	O
emulating	O
the	O
original	O
games	O
.	O
</s>
<s>
TouchArcade	O
has	O
referred	O
to	O
the	O
remasters	O
of	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
and	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
2	I-Application
as	O
"	O
spectacular	O
"	O
.	O
</s>
<s>
Whitehead	O
has	O
named	O
games	O
such	O
as	O
Ristar	B-Application
,	O
Knuckles	B-Application
 '	I-Application
Chaotix	I-Application
,	O
and	O
Dynamite	B-Application
Headdy	I-Application
,	O
as	O
well	O
as	O
non-Sega	O
games	O
like	O
the	O
Castlevania	B-Application
series	O
,	O
as	O
others	O
that	O
would	O
be	O
possible	O
to	O
port	O
to	O
the	O
engine	O
.	O
</s>
