On 14 May 2015, U2 embarked on a worldwide concert tour called the Innocence + Experience Tour. It was U2's first time playing arenas since 2005–2006 on their Vertigo Tour. Comprising 76 shows over two legs, the tour visited North America from May through July, and Europe from September through December. The band structured their concerts around a loose narrative of "innocence" passing into "experience", with a fixed set of songs for the first half of each show and a varying second half, separated by an intermission–a first for U2 concerts. The stage spanned the length of the venue floor and comprised three sections: a rectangular segment that illuminated as an "I" to represent "innocence"; a smaller circular stage that illuminated as an "e" to represent "experience"; and a walkway between them to represent the transition between the two themes. A double-sided video screen was suspended above and parallel to the walkway; the structure featured an interior catwalk between the screens, allowing the band members to perform amidst the video projections. U2's sound system was moved to the venue ceilings and arranged in an oval array, in hopes of improving acoustics by evenly distributing sound throughout the arena. In total, the tour grossed $152.2 million from 1.29 million tickets sold. The final date of the tour, one of two Paris shows rescheduled due to the 13 November 2015 attacks in the city, was filmed for the video "" and broadcast on the American television network HBO.