Why has the ball changed for World Cup semi-finals?

[BBC] Fifa has introduced a new ball for the last four games of the World Cup. The gold and black Trionda Final ball will be used during the two semi-finals - France v Spain and England v Argentina, the third-place play off and Sunday's World final. On 6 July, Adidas and Fifa announced it would replace the Trionda Official Match ball, which adopted the colours of the host countries of red, blue, green and white and was used for the first 100 games of the tournament. The name 'Trionda' can be translated from Spanish as 'three waves' and represents the three host countries. The Trionda final ball will be used in the World Cup semi-finals, bronze final and final [Getty Images] Fifa said: "Uniquely, Trionda Final celebrates the 16 iconic host cities that have welcomed the world for the biggest Fifa World Cup ever. "As host of the semi-finals, bronze final and final, Dallas, Atlanta, Miami and New York New Jersey are prominently featured within the main blocking of the design. "Meanwhile, Boston, Guadalajara, Houston, Kansas City, Los Angeles, Mexico City, Monterrey, Philadelphia, San Francisco Bay Area, Seattle, Toronto and Vancouver are incorporated within the triangular graphic elements, ensuring their significant contributions to the success of the tournament are recognised right through to the final whistle." Fifa says the final ball has up-to-date AI technology "delivering precise ball data in real time to support faster decision-making by match officials, while enhancing insights into the game". This article is the latest from BBC Sport's Ask Me Anything team. More questions answered... What is the perfect age to win the World Cup? Who are the World Cup's record holders? Should teams bring on players just for penalty shootouts?