Had a Sunday afternoon free, couldn't resist banging something together with whatever I could scrounge from the dustbin outside. Looks pretty cool!:

Next, I'll make some proper slide rails, re-build the frame out of something better, add the LASER (a 500mW IR one) and generally make it all better.

The code as it stands - very obviously hacky, will get better:

/*
Enable turtle-like control of an etch-a-sketch like 2 axis stepper
thingee. Penup/pendown can be, for eg, laser on or off etc.

Code by Jonathan Whitaker, MIT licence

*/

//Settings for motor stuff
int delay_time = 200; //ms, lengthen for debugging
int xsize = 2000; //number of steps possible in the X direction
int ysize = 2000; //""Y""

//Store Position etc
int posX = 0; //start bottom left
int posY = 0;

//Instructions - the biggie
int instructions[] = {'F 100', 'R 90', 'F 100'};

//Pins for steppers 1 and 2
int s1s = 3; //stepper 1 step
int s1d = 2; //direction
int s2s = 6;
int s2d = 7;
//Pins for LASER!!!! Sharks to follow in version 42
int lpin = 2;
//all together now
int out_pins[] = {s1s, s1d, s2s, s2d, lpin};
int out_pin_count = 5;

// Setup stuff, pretty self-explanatory
void setup() {
for (int i=0;i<out_pin_count;i++){
pinMode(out_pins[i], OUTPUT);
}
}

void loop() {
square();
delay(5000);
}

//step x and y by a certain amount.
void step_by(int stepsx, int stepsy){
//sort out directions
if (stepsx < 0){
digitalWrite(s1d, LOW);
stepsx = (0-stepsx);
}
else{
digitalWrite(s1d, HIGH);
}
if (stepsy < 0){
digitalWrite(s2d, LOW);
stepsy = (0-stepsy);
}
else{
digitalWrite(s2d, HIGH);
}

//figure out which one is bigger - we will step that one each cycle
//then we'll step the other one only when d(small)/d(large) hits the next integer
if (stepsx > stepsy){
int prev_int_y = 0;
for (int i = 0; i < stepsx; i++){
digitalWrite(s1s, HIGH); //always step X
if (floor((i*(stepsy/stepsx)))>prev_int_y){
prev_int_y = floor((i*(stepsy/stepsx))); //keep track of last int jump
digitalWrite(s2s, HIGH); //step Y
}
delayMicroseconds(delay_time);
digitalWrite(s1s, LOW);
digitalWrite(s2s, LOW);
}
}
//the same thing again - remember to propagate changes for now, next time do the damn job properly!
if (stepsy >= stepsx){
int prev_int_x = 0;
for (int i = 0; i < stepsy; i++){
digitalWrite(s2s, HIGH); //always step X
if (floor((i*(stepsx/stepsy)))>prev_int_x){
prev_int_x = floor((i*(stepsx/stepsy))); //keep track of last int jump
digitalWrite(s1s, HIGH); //step Y
}
delayMicroseconds(delay_time);
digitalWrite(s1s, LOW);
digitalWrite(s2s, LOW);
}
}
}

//need a goto_pos(x, y) function, plus fill in circle and square
void go_to(int xpos, int ypos){
step_by((xpos-posX), (ypos-posY));
}

void circle() {
// go to center, out 300, draw a circle
for (int i = 0;i < 360;i++){
step_by(floor(20*sin(i/360.0)), floor(20*cos(i/360.0)));
}
}

void square(){
step_by(0, 2000);
step_by(2000, 0);
step_by(0, -2000);
step_by(-2000, 0);
//go to 100, 100
//go_to(100, 100);
// go_to(300, 100);
// go_to(300, 300);
// go_to(100, 300);
}