Kieran Tierney bombed up the left flank and Scott Sinclair moved inside to join Leigh Griffiths, with the visitors unable to cope with the movement.Without a recognised frontman for the majority of the previous round clash with Rosenborg, Celtic toiled to break down their opponents.Leigh Griffiths’ return on Wednesday was welcome.The Scottish striker was a constant menace to Astana’s centre-backs, showing clever movement and a composed touch to become the focal point to the Scottish champions’ attacks.By running in behind, Griffiths stretched the play and opened up space for Tom Rogic and Scott Sinclair to exploit, with both taking advantage.Controversy: Referee Ovidiu Hategan waved play on after a clash of heads. SNSCeltic’s third goal was scored amid controversy.Scott Sinclair bagged his second of the night on the hour mark as a player from each side lay stricken on the turf following a head clash.Romanian referee Ovidiu Hategan was in position but waved play on and Griffiths slipped for Sinclair to convert.Astana manager Stanimir Stoilov said: “If I were the referee I would have stopped the game. First of all, we have to think about the health and safety of the players.”Celtic’s “ultras” group the Green Brigade also missed the Rosenborg tie but were back on Wednesday after club sanctions were fully lifted.They marked their return with a new tifo inspired by UFC star Conor McGregor and helped create a boisterous atmosphere in which the Celtic players thrived.As the rain poured down in Glasgow’s east end Astana succumbed to a deluge of Celtic attacks on the pitch and a flood of goals went in.After Tom Rogic waltzed through as Celtic opened the scoring, the away side looked unsure whether to press for an away goal or shut up defensively ahead of the second leg.In the end they managed neither and collapsed to a catastrophic defeat that all but ends their Champions League dream for another season. One year and the improvements are clear for all to see.With Rodgers’ ideas for the Hoops embedded, Celtic played in a fluid attacking manner that proved too hot for the Astana back-line to handle.Defensively, Celtic set up with a conventional back four with Israeli midfielder Nir Bitton once again dropping back and excelling.When possession was recovered the home side moved to three defenders. Celtic produced a five-star showing to sweep aside Astana and all but book their place in the Champion’s League group stage.In front of a raucous Parkhead support Brendan Rodgers’ side overwhelmed their opponents to ensure they take a comprehensive lead with them on the 6000-mile round-trip to Kazakhstan.Here we look back at the key talking points from a huge Euro win for the Hoops – Celtic’s improvement, Griffiths leading the line, the return of the Green Brigade and refereeing controversy.Last year’s ride towards Champion’s League qualification was a bumpy one for the Celtic support following Brendan Rodgers appointment as the side tried to implement the Northern Irishman’s playing style.