 Complete the following phrase:  On 14 May 2015, U2 embarked on a worldwide concert tour called the Innocence  Experience Tour. It was U2s first time playing arenas since 20052006 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 intermissiona 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. U2s 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 