Added body to readme

Author: xunker

README.md

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 # eclipse_simulator
+
+Visualizers to show sun and moon positions, give a certain time and position on
+the earth. Two examples are present, using Gosu and Ruby2D.
+
+To install the gosu and ruby2d gem you will also need the following libraries:
+* gosu (brew install gosu on macos)
+* sdl2 (brew install sdl2 on macos)
+* simple2d (`brew tap simple2d/tap; brew install simple2d` on macos)
+
+After installing the gems, do `bundle install` an normal.
+
+The green line is the horizon and will move up and down depending on the time
+of the year.
+
+Default starting position on the earth is Grand Teton National Park, which
+will be in the path of totality for the 2017 Eclipse. Default time is the
+projected time of totality for that location.
+
+You can move through time with the left and right arrows. By default, right
+arrow will move you 1 hour ahead, left will move you one hour behind. You can
+change the movement speed using the up and down arrows. Your current movement
+speed is shown in the window title bar.
+
+The "r" key will set the time to be sunrise of the current day.
+
+The "s" key will set the time to be sunset of the current day.
+Escape will exit.
+
+You can change the position on earth by changing the value of `@coords`:
+Insert your preferred Lat/Long coordinates in decimal format.
+
+You can also change the default start time by changing `@current_time`. You can
+also uses the SunCalc gem to set the time to be sunrise, sunset, mid-day, etc.