Becky

 One way to make me perk right up: reference the Into the Void opening credits in your movie's opening credits*. Do it on a notebook with animated teen doodles, as Becky does, and we're in business.

 Becky Hopper (Lulu Wilson) is a sullen thirteen-year old girl who's still mourning her mother a year after bereavement. She's a troubled girl, introduced as she's bullied at school and seemingly implied to be somewhere in the spectrum on some of the early scenes. She's bright and pretty funny, but you can imagine how hard it would be to live with someone as a parent.

 Pity her dad, then, for trying to move on. He takes Becky on holiday to a beloved lakeside cabin, and spoils everything by inviting his new girlfriend Kayla (Amanda Brugel) over... and telling his daughter he intends to re-marry. It goes as well as you'd expect.

 After Becky's run away to her hiding spot to brood, a murderous neo-nazi gang freshly escaped from prison and led by one Dominick (Kevin James) takes over the cabin looking for a key they'd hidden before they were put away. A key (marked with a proto-germanic symbol) that, of course, Becky has found and taken for herself.
 Kind of a Die Hard situation, then, with a (record scratch) thirteen-year-old girl wearing a cute woven animal hood in the McLane role. And it works brilliantly! Mostly because the character of Becky reminded me more of a latter-day Liam Neeson action role more than a Bruce Willis one, but on the opposite end of the unlikely-age spectrum.

 It's a stew of genres and influences: an indie drama frequently checking in on Becky's memories of her mother, a thriller with some very effective, tense scenes, a sprinkling of extremely bloody action. Home Alone and the aforementioned Neeson vehicles are a reference point, and it invokes the ghost of a slasher movie with its bloodlust and music (a cheeky, lively Friday the 13th-ish mix of music and breathy panting). I think my favorite thing about it is that despite having a rich seam of bloody gallows humor, the film plays all of its elements dead straight.

 The premise may be silly, but it's mostly rendered plausible by the way the script (by Nick Morris and Ruckus & Lane Skye) grounds its elements. The protagonist's shift from terrified teen to deranged killer feels earned, and the progression of events makes sense. The action is brutal and takes into account Becky's physical disadvantage at all times; She does spring back a little too quickly after being brutally manhandled, and also ignores a convenient gun at one point, but that's well within genre conventions.

 There are a few instances of overt humor here and there (the most obvious a rambo-2-referencing 'suiting up' montage that involves a star-shaped mirror) but that's pretty rare; most laughs come instead from how extreme things get.

 The filmmaking is great, with the cinematographer (Greta Zoula), editor (Alan Canant)  and directors (Jonathan Milott and Cary Murnion) staging some elaborate scenes that cut between, say, the thugs escaping and some fragments of Becky's school life, or getting creative when Becky and Dominick talk over walkie-talkies. The film gets more traditional as it progresses, but things are always cleanly staged. The music (by Nima Fakhrara) is a good mix between ambiental Indie music and crazy mix of vocals and instrumental weirdness.

 And while all the actors are good in this, both Lulu Wilson and Kevin James do an excellent job with their characters; Wilson really sells both Becky's pain and her psycho determination, and James displays the sort of cult-leader charisma you'd expect out of his Manson-like character. The guy's deluded enough that he thinks he can win Becky over with a "we are not so different, you and I" spiel near the end.
 I also really liked his second in command Apex (Robert Maillet), who has a significant role as the lone thug with a little humanity. 

 Cap it off with some extreme levels of gore - wet, chunky, and detailed, more so than most horror movies (the FX crew clearly pulled out medical reference texts for this one), and we've got something special on our hands. It's a simple movie, but a wildly, viciously entertaining one.

*: Or maybe they're more indebted to Spiderverse, but I choose to think otherwise.