// From the book

module led_toggle (
  input clk_i,
  input key_i,
  output [5:0] led
);

reg r_LED_1 = 1'b1;
reg r_Switch_1 = 1'b1;

always @(posedge clk_i) begin
  r_Switch_1 <= key_i;
  if (key_i == 1'b1 && r_Switch_1 == 1'b0) begin
    r_LED_1 <= ~r_LED_1;
  end
end

assign led[0] = r_LED_1;
assign led[5:1] = 5'b11111;

endmodule