You can use all Lua functions from http://www.lua.org and the following special PSP Lua Player functions for your script.lua:
Return the current bitmask of the buttons. Use the isCtrl*-functions to check
which button is pressed.
Return true, if the bit for the select key is set in the bitmask.
Return true, if the bit for the start key is set in the bitmask.
Return true, if the bit for the up key is set in the bitmask.
Return true, if the bit for the right key is set in the bitmask.
Return true, if the bit for the down key is set in the bitmask.
Return true, if the bit for the left key is set in the bitmask.
Return true, if the bit for the up key is set in the bitmask.
Return true, if the bit for the left trigger is set in the bitmask.
Return true, if the bit for the right trigger is set in the bitmask.
Return true, if the bit for the triangle key is set in the bitmask.
Return true, if the bit for the circle key is set in the bitmask.
Return true, if the bit for the cross key is set in the bitmask.
Return true, if the bit for the square key is set in the bitmask.
Return true, if the bit for the home key is set in the bitmask.
Return true, if the bit for the hold key is set in the bitmask.
Wait for next Vblank start. If you specify a count parameter, it waits multiple times for Vblank start. This can be used for delays, for example 60 for a one seconds delay.
Flip the current drawing offscreen with the display screen.
Blit an image to screen or into another image, if destinationImageHandle is specified. Alpha channel is ignored.
Blit an image to screen or into another image, if destinationImageHandle is specified.
sx: left position of rectangle in source image
sy: top position of rectangle in source image
width: width of rectangle in source image
height: height of rectangle in source image
imageHandle: the source image
dx: left target position in destination image or screen
dy: top target position in destination image or screen
destinationImageHandle: destination image, if specified
Blit a part of an image to screen or into another image, if
destinationImageHandle is specified. Alpha channel is ignored.
Same as blitImageRect, but with alpha channel.
Fill a rectangle.
Create an empty image.
Clear an image or screen.
Save a screenshot in the game directory in TGA format.
Load an image in the game directory in PNG format.
Get the width of an image.
Get the height of an image.
Put a pixel on an image or on screen.
Get the color of an pixel of an image or screen.
Print a decimal number as 7 segment.
Print a text at the specified position
Return the color for using with putPixel, clear and fillRect (opaque is set for alpha)
Return the entries of the current directory or of path, if specified, or nil,
if an error occured
Return the current directory.
Change the current directory
Draw a line.