<s>
Ballerburg	B-Application
is	O
a	O
turnbased	O
Artillery	B-Application
game	I-Application
from	O
1987	O
,	O
written	O
in	O
C	B-Language
by	O
Eckhard	O
Kruse	O
for	O
the	O
Atari	B-Device
ST	I-Device
.	O
</s>
<s>
The	O
game	O
was	O
distributed	O
free	O
of	O
charge	O
as	O
public	B-Application
domain	I-Application
software	I-Application
.	O
</s>
<s>
It	O
was	O
also	O
donationware	B-License
as	O
the	O
author	O
asked	O
for	O
donations	O
of	O
20	O
DM	O
,	O
offering	O
as	O
incentive	O
the	O
source	O
code	O
for	O
the	O
game	O
.	O
</s>
<s>
Ballerburg	B-Application
was	O
designed	O
for	O
two	O
players	O
,	O
both	O
of	O
which	O
can	O
be	O
human	O
or	O
computer-controlled	O
.	O
</s>
<s>
Years	O
later	O
,	O
in	O
October	O
2004	O
,	O
the	O
author	O
released	O
the	O
game	O
with	O
source	O
code	O
for	O
free	B-License
download	I-License
on	O
his	O
website	O
(	O
public	B-Application
domain	I-Application
software	I-Application
)	O
.	O
</s>
<s>
The	O
source	O
code	O
availability	O
resulted	O
in	O
several	O
ports	O
to	O
other	O
systems	O
with	O
SDL	B-Operating_System
,	O
for	O
instance	O
to	O
Windows	O
,	O
Linux	B-Application
,	O
and	O
Mac	B-Application
OS	I-Application
.	O
</s>
<s>
In	O
April	O
2012	O
,	O
on	O
the	O
25th	O
birthday	O
of	O
the	O
game	O
,	O
an	O
iOS	B-Application
port	O
was	O
released	O
,	O
endorsed	O
by	O
the	O
original	O
author	O
.	O
</s>
<s>
In	O
2001	O
there	O
was	O
another	O
game	O
by	O
Ascaron	O
,	O
without	O
endorsement	O
of	O
Kruse	O
,	O
under	O
the	O
name	O
Ballerburg	B-Application
.	O
</s>
