One minute they are running about their apartment block stairwell passing a sign saying "Level 5" then, a couple of minutes and flights later, they reach the roof on level 24.
Despite being repeatedly blown up and shot at by the aliens, Alice's make-up is still utterly flawless at the 45-minute mark.
Why weren't the supposedly intelligent leaders who remained aware that the enemy would return not better prepared? They had decades to get ready and the best they could come up with was automatic rifles and hiding to fight another day (while the enemy was entrenched)? It's not science fiction when characters are that stupid. It's a tricked-out horror film.