<s>
Gravity	B-Application
Ghost	I-Application
is	O
a	O
physics	O
based	O
puzzle	O
game	O
created	O
by	O
indie	O
developer	O
Ivy	O
Games	O
.	O
</s>
<s>
It	O
was	O
released	O
on	O
Microsoft	B-Application
Windows	I-Application
,	O
macOS	B-Application
,	O
and	O
Linux	B-Application
on	O
26	O
January	O
2015	O
.	O
</s>
<s>
In	O
Gravity	B-Application
Ghost	I-Application
,	O
the	O
player	O
controls	O
the	O
ghost	O
of	O
a	O
young	O
girl	O
named	O
Iona	O
,	O
who	O
flies	O
through	O
a	O
fantasised	O
version	O
of	O
space	O
(	O
analogous	O
with	O
purgatory	O
)	O
with	O
her	O
friend	O
,	O
a	O
ghost	O
fox	O
.	O
</s>
<s>
The	B-Operating_System
PlayStation	I-Operating_System
4	I-Operating_System
version	O
was	O
released	O
on	O
6	O
August	O
2019	O
.	O
</s>
<s>
Unable	O
to	O
find	O
an	O
antidote	O
on	O
the	O
island	O
,	O
Iona	O
's	O
parents	O
rush	O
to	O
the	O
mainland	O
through	O
a	O
stormy	O
night	O
,	O
tasking	O
Arthur	O
to	O
maintain	O
the	O
lighthouse	B-Application
light	O
for	O
their	O
return	O
later	O
in	O
the	O
night	O
.	O
</s>
<s>
As	O
Arthur	O
waits	O
at	O
the	O
top	O
of	O
the	O
lighthouse	B-Application
,	O
lightning	O
strikes	O
it	O
,	O
shattering	O
the	O
lens	O
,	O
incapacitating	O
Arthur	O
and	O
dooming	O
Iona	O
's	O
parents	O
to	O
crash	O
.	O
</s>
<s>
Hickory	O
has	O
become	O
an	O
astronomer	O
,	O
and	O
when	O
she	O
discovers	O
a	O
periodic	O
comet	B-Language
,	O
she	O
names	O
it	O
Iona	O
's	O
comet	B-Language
.	O
</s>
<s>
The	O
comet	B-Language
has	O
an	O
orbital	O
period	O
of	O
twelve	O
years	O
,	O
the	O
age	O
which	O
Iona	O
was	O
at	O
the	O
time	O
of	O
her	O
death	O
.	O
</s>
