How to make a puzzle game

[BraveVN]

Guys/girls, I’m making a 2D puzzle game for kids which they can drag small pieces (there are many kind of shapes like square, rectangle, triangle, circle, L-shape, half moon…) and drop them to a big shape to fill it up (the shape may be a polygonal).

The question is how can I make the orange piece become auto fit to every edges of square when the shape is near the edges, like the situation when we hover a metal piece close to a magnet and it’s sticked.

Further more, I use OnMouseDrag() function to drag and drop objects, it works good on PC with mouse but when I build on mobile device, may be it also works on touch screen ?

Thank you.

Edit: All pieces and shapes are 2D sprites

[fafase]

(This is using words from new UI but is not related)

Your canvas (the grey rectangle) should have anchor points, simply some empty game objects (Transform). When the button is released you would check if the orange piece is close enough to any of those anchor points and if so you start a lerp process to the point, or you snap there.

private Transform[] anchor;
private Transform target = null;
void Start()
{
    anchor = Manager.GetAnchor(); // This returns the array of anchor you defined somewhere else
}
void Update()
{
    if(lerp)
    {
        transform.position = Vector3.MoveTowards(transform.position, target.position, ratio);
        if(transform.position == target.position){lerp = false;}
    }
    // More code
}
void OnMouseUp()
{
     target = GetAnchor();
     if(target != null)   
     {
         lerp = true;
     }
}

private Transform GetAnchor()
{
   Transform closest = null;
   float distance = Mathf.Infinity;
   float range = 0.2f;
   foreach(Transform t in anchor)  // iterate all anchors
   {
        float dist = Vector3.Distance(transform.position, t.position);
        if(dist < range && dist < distance) // check if close enough and closer than any other already checked points.
        {
              closest = t;
              distance = dist;
        }
   }
   return closest;
}