See the following URL for SDL requirements:-

http://aminet.net/package/dev/misc/SDL-Amiga


XGALAGA-SDL version date:-  2013-04-25


XGalaga-SDL is a port of the popular X11 game XGalaga, a clone of Galaga,
using the SDL (Simple DirectMedia Layer) library. XGalaga was originally
written by Joe Rumsey.


Keyboard commands:

  p - pauses
  q - end this game
  s - toggle sound if your system supports it

  Controls: left_arrow  - move left
            right_arrow - move right
            space_bar   - fire


http://sourceforge.net/projects/xgalaga-sdl/


Credits:
   Galaga code:
            Joe Rumsey (mrogre@mediaone.net)
   X interface:
            Bill Dyess(dyessww@eng.auburn.edu),
            Rob Forsman(thoth@cis.ufl.edu),
            and about a million others.

   Sound server/interface:
            Sujal Patel (smpatel@wam.umd.edu)
            Paul Kendall (paul@kcbbs.gen.nz) (Sun and NAS support)

   Pixmaps:
            Joe Rumsey (ogre@atomic.com)
            Mike McGrath (mcgrath@epx.cis.umn.edu)

   SDL port:
            Andy Tarkinson
            Frank Zago
            Dan Espen


Feeling bored ?  :)
Why not check out this URL ?

http://home.iprimus.com.au/lombi/1/homepage.htm

PERMISSION  UID  GID    PACKED    SIZE  RATIO METHOD CRC     STAMP     NAME
---------- ----------- ------- ------- ------ ---------- ------------ ----------
[unknown]                 1841    2802  65.7% -lh5- b1ad Aug 27 01:03 xgalaga.info
[unknown]                   66     280  23.6% -lh5- 656e Aug 26 22:43 xgalaga/.xgalaga-sdl
[unknown]                 1842    2802  65.7% -lh5- 2814 Aug 27 01:04 xgalaga/docs.info
[unknown]                 6996   18092  38.7% -lh5- a33a Mar 24  2010 xgalaga/docs/COPYING
[unknown]                  256     487  52.6% -lh5- 26a7 Aug 27 01:04 xgalaga/docs/COPYING.info
[unknown]                  667    1204  55.4% -lh5- e7c0 Mar  6  2008 xgalaga/docs/CREDITS
[unknown]                  256     487  52.6% -lh5- 8281 Aug 27 01:04 xgalaga/docs/CREDITS.info
[unknown]                 1385    2734  50.7% -lh5- 127f May  1  2011 xgalaga/docs/README
[unknown]                  258     487  53.0% -lh5- cf1b Aug 27 01:04 xgalaga/docs/README.info
[unknown]                  619    1109  55.8% -lh5- 082e Jun  4  2010 xgalaga/docs/xgalaga-sdl.6x
[unknown]                  236     468  50.4% -lh5- bed0 Aug 27 01:04 xgalaga/docs/xgalaga-sdl.6x.info
[unknown]                  801    1446  55.4% -lh5- d15e Aug 27 01:32 xgalaga/docs/xgalaga_68k.readme
[unknown]                  239     487  49.1% -lh5- 344f Aug 27 01:04 xgalaga/docs/xgalaga_68k.readme.info
[unknown]                 1067    1452  73.5% -lh5- 5096 Nov 12  2011 xgalaga/IconX
[unknown]                  426     426 100.0% -lh0- 14dc May 16  2010 xgalaga/images/al.png
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[unknown]                  359     370  97.0% -lh5- a766 May 17  2010 xgalaga/images/pr_machine.png
[unknown]                  384     384 100.0% -lh0- 0d73 May 16  2010 xgalaga/images/pr_shield.png
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[unknown]                  333     354  94.1% -lh5- 0078 May 17  2010 xgalaga/images/pr_spread.png
[unknown]                  356     356 100.0% -lh0- 505b May 16  2010 xgalaga/images/pr_trip.png
[unknown]                  293     318  92.1% -lh5- e66f May 16  2010 xgalaga/images/s1000.png
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[unknown]                 1989    2001  99.4% -lh5- 9bdc May 16  2010 xgalaga/images/title.png
[unknown]                  502    1670  30.1% -lh5- 3d16 Mar  6  2008 xgalaga/levels/level1.xgl
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[unknown]                  511    1904  26.8% -lh5- 96e9 May 16  2010 xgalaga/sounds/ddloo.wav
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[unknown]               184929  184929 100.0% -lh0- 2e1c Aug 27 01:25 xgalaga/src.tar.7z
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[unknown]                  229     460  49.8% -lh5- 077e Aug 27 01:03 xgalaga/xgalaga.info
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 Total        91 files  751443  845511  88.9%            Sep  6 20:03