symbols (addition) (asteriskoperator bmp (bitmapimage files (concatenation operator) - (division) =(equality operator) (greater than) >(greater than or equal to) (hash mark)for comments !(inequality operator) (less than) <(less than or equal to) (modulo operator) - (multiplication) \ (newline) (not) +operator py file extension [(square brackets) (subtraction) \ (tab) addition (+) aliases alice py - alien invasion project see also pygame aliens alien class building fleet of - changing directions checking edges creating creating rows of drawing to the screen dropping fitting in row movement - multiple rows of reaching bottom of screen rebuilding fleet of background colorsetting bullets bullet class - checking with print statements deleting old firing limiting the number of making larger settings speeding up classes alien bullet - button scoreboard settings ship collisions alien-bullet alien-ship - ending game - keyboard shortcuts levels adding - modifying speed settings resetting speeds planning