import java.awt.*
import javax.swing.*

fun main() {
   SwingUtilities.invokeLater {
      val panel  = object: JPanel() {
         override fun paintComponent(g: Graphics) {
            super.paintComponent(g)
            val scale = 4;
            for (i in 0..63) {
               g.setColor(
                  Color(i * 4, 0, 255 - i * 4))
               g.fillRect(i * scale, 0, scale, 40) 
            }
         }
      }
      panel.setPreferredSize(Dimension(256, 40))  
   
      val frame = JFrame("Gradation")
      frame.add(panel)
      frame.pack()
      frame.setDefaultCloseOperation(
         JFrame.EXIT_ON_CLOSE)
      frame.setVisible(true)
   }
}