LUA TURTLE

Movement

• forward(n)Move forward n pixels. Alias: fd
• back(n)Move backward n pixels. Alias: bk
• left(degrees)Turn left. Alias: lt
• right(degrees)Turn right. Alias: rt
• setpos(x, y)Move to coordinates (x, y)
• setheading(angle)Face a direction (0=east, 90=north). Alias: seth
• home()Return to center, face east
• setx(x)Set x coordinate, keep y
• sety(y)Set y coordinate, keep x
• teleport(x, y)Jump to position instantly, no drawing

Pen

• penup()Stop drawing. Alias: pu
• pendown()Start drawing. Alias: pd
• pensize(n)Set line width
• pencolor(r, g, b)Set color with RGB (0–1 or 0–255)
• pencolor("name")Set color by name: "red", "blue", "gold", etc.
• color("red")Set both pen and fill color
• color("red", "blue")Set pen and fill color independently

Shapes

• circle(radius)Draw a full circle
• circle(radius, extent)Arc: extent in degrees

Fill

• begin_fill()Start recording a filled shape
• end_fill()Fill the shape drawn since begin_fill
• filling()Returns true if currently filling
• fillcolor(r, g, b)Set fill color
• dot(size)Draw a filled circle at turtle's position
• dot(size, "red")Draw a dot with a specific color

Text

• write(text)Write text at turtle's position
• write(text, move, align, font)align: "left", "center", "right"; font: {family, size}

Canvas

• bgcolor(r, g, b)Set background color
• bgcolor("name")Set background color by name
• screen_width()Returns canvas width in pixels
• screen_height()Returns canvas height in pixels
• clear()Erase drawing, keep turtle position
• reset()Erase drawing and reset turtle to start
• undo()Undo the last command
• setundobuffer(n)Set max undo history length
• speed(n)0=instant, 1=slowest, 10=fastest

Graphing

• graph(left, bottom, right, top)Use graph coordinates: this rectangle, one unit the same length both ways
• graph(left, bottom, right, top, "stretch")Graph coordinates stretched to fill the canvas
• graph(left, bottom, right, top, box)A graph in a box: {x, y, width, height, units}; the rest of the canvas keeps its coordinates
• setworldcoordinates(left, bottom, right, top)Make the canvas edges these coordinates, as in Python
• axes()Draw graph paper: grid, axes and numbers
• axes(xstep, ystep, xname, yname)Grid lines every xstep and ystep; name the axes
• plot(f, color)Draw the curve y = f(x) across the graph
• mark(x, y, color, label)Draw a dot at (x, y), with a label
• g:plot(f, color)Draw on graph g even after a newer graph(); g:axes() and g:mark(x, y) too
• g:tocanvas(x, y)The canvas point at (x, y) on graph g, for the turtle: setpos(g:tocanvas(2, 3))
• g:tograph(x, y)The point on graph g at canvas point (x, y), such as a click

Interaction

• onclick(f)Call f(x, y) when the canvas is clicked
• ondrag(f)Call f(x, y) as the pointer drags across the canvas
• onrelease(f)Call f(x, y) when the pointer lets go of the canvas
• onkeypress(f, key)Call f when key is pressed; leave out key for any key
• onkeyrelease(f, key)Call f when key is let go. Alias: onkey
• done()Keep answering clicks, keys and controls until Stop; code after it waits. Alias: mainloop
• slider(options)A slider: {label, min, max, value, step, x, y, width, onchange}; read s.value
• button(options)A button: {label, x, y, width, onclick}
• toggle(options)An on/off switch: {label, value, x, y, onchange}; read t.value
• radio(options)Radio buttons: {label, options, value, x, y, onchange}; read r.value
• textfield(options)A text box: {label, value, x, y, width, onchange, onsubmit}; read f.value
• control.valueRead or set a control's value as the program runs; control.label likewise
• control:remove()Take a control off the canvas

Turtle

• hideturtle()Hide the turtle. Alias: ht
• showturtle()Show the turtle. Alias: st
• stamp()Stamp turtle shape; returns id
• clearstamp(id)Remove a stamp
• clearstamps(n)Remove last n stamps; omit n to clear all
• Turtle()Create a second turtle with all the same methods

State Queries

• position()Returns x, y coordinates
• xcor() / ycor()Returns x or y coordinate
• heading()Returns current angle in degrees
• isdown()Returns true if pen is down
• isvisible()Returns true if turtle is visible
• distance(x, y)Returns distance to point
• towards(x, y)Returns angle towards point