Step one:
First draw a rectangle.
Step 2:
Then draw a circle underneath.
Step 3:
Draw two more arcs above and connect them to form a lead.
Step 4:
Inside the leader line, draw a little arc as texture.
Step 5:
Use small polylines to draw sparks at the end, and add a few small dots.
Step Six:
Add highlights and a little decorative line to it.
Step 7:
Finally, apply a nice color and the bomb is ready.