Match-winning Miroslav Klose marked his 28th birthday with a pair of gift-wrapped goals against Costa Rica on Friday.
Then, as the celebrations began, he warned the hosts' rivals that Germany can only improve as the tournament unfolds.
Klose, top scorer in the Bundesliga last season, continued his personal speciality of scoring freely in Germany's opening World Cup fixtures with goals after 17 and 61 minutes in their 4-2 triumph.
It was the highest-scoring opening fixture in the history of the World Cup.
He hit a hat-trick four years ago as the Germans thumped Saudi Arabia 8-0 in Sapporo in their opening game.
"Yes, it seems to be a habit," he said with a smile. "But of course this feels great -- to play at home, in the opening match of the World Cup finals in your own country and to score two goals -- it could not be better.
"But the most important thing was for us to win the match. Now we know we can score goals but we know we can improve our performance and I am very confident we can do that."
Klose was withdrawn after 79 minutes to a standing ovation from the sell-out capacity crowd of 66,000 at the Allianz Arena.
He said he had been feeling a slight tension in his left thigh, but it was not enough to trouble his fitness for the Germans' next game against Poland in Dortmund on June 14.
"This, today, has given me a beautiful feeling," said Klose, who was chosen by FIFA's panel of experts as the man of the match.
Klose denied that the German defence, which conceded two goals created by inter-passing by the Costa Rican forwards, was a cause for concern.
"No," he said. "It is not the fault of the defence. When we lose possession, in attack, we have to fight to get behind the ball again. We didn't do that. We made it difficult for them. It was our fault."
He said he had not celebrated either of his goals with a characteristic somersault on Friday because they were not really important enough.
"I just do those flip-ups now when it is a very beautiful, very important goal -- so I hope you will see a few in this tournament."