Create a random polygon every time you touch the canvas.

C4WorkSpace.m

//
//  C4WorkSpace.m
//  Examples
//
//  Created by Travis Kirton.
//

#import "C4WorkSpace.h"

@implementation C4WorkSpace {
    C4Shape *s;
}

-(void)setup {
    CGPoint pts[10];
    for(int i = 0; i < 10; i++) {
        pts[i] = CGPointMake([C4Math randomInt:386], [C4Math randomInt:386]);
    }
    
    s = [C4Shape polygon:pts pointCount:10];
    s.lineWidth = 20.0f;
    s.center = self.canvas.center;
    [self.canvas addShape:s];
}

-(void)touchesBegan {
    CGPoint pts[10];
    for(int i = 0; i < 10; i++) {
        pts[i] = CGPointMake([C4Math randomInt:386], [C4Math randomInt:386]);
    }
    [s polygon:pts pointCount:10];
}

@end