diff --git a/.cargo/config.toml b/.cargo/config.toml
new file mode 100644
index 0000000..03f4879
--- /dev/null
+++ b/.cargo/config.toml
@@ -0,0 +1,2 @@
+[build]
+rustflags = ["-Ctarget-cpu=native"]
diff --git a/src/day16.rs b/src/day16.rs
index 2d9e98a..53481fd 100644
--- a/src/day16.rs
+++ b/src/day16.rs
@@ -8,8 +8,8 @@ fn split_once<'a>(input: &'a str, delimeter: &str) -> Option<(&'a str, &'a str)>
 
 struct Rule<'a> {
     name: &'a str,
-    a: RangeInclusive<usize>,
-    b: RangeInclusive<usize>,
+    a: RangeInclusive<u16>,
+    b: RangeInclusive<u16>,
 }
 impl<'a> Rule<'a> {
     fn parse(input: &'a str) -> Option<Self> {
@@ -17,22 +17,22 @@ impl<'a> Rule<'a> {
         let (a, b) = split_once(rem, " or ")?;
         let a = {
             let (start, end) = split_once(a, "-")?;
-            RangeInclusive::<usize>::new(start.parse().ok()?, end.parse().ok()?)
+            RangeInclusive::<u16>::new(start.parse().ok()?, end.parse().ok()?)
         };
         let b = {
             let (start, end) = split_once(b, "-")?;
-            RangeInclusive::<usize>::new(start.parse().ok()?, end.parse().ok()?)
+            RangeInclusive::<u16>::new(start.parse().ok()?, end.parse().ok()?)
         };
         Some(Rule { name, a, b })
     }
 
-    fn matches(&self, value: usize) -> bool {
+    fn matches(&self, value: u16) -> bool {
         self.a.contains(&value) || self.b.contains(&value)
     }
 }
 
 #[aoc(day16, part1)]
-fn solve_d16_p1(input: &str) -> usize {
+fn solve_d16_p1(input: &str) -> u16 {
     let (rules, rem) = split_once(input, "\n\nyour ticket:\n").unwrap();
     let (_your_ticket, nearby_tickets) = split_once(rem, "\n\nnearby tickets:\n").unwrap();
 
@@ -41,7 +41,7 @@ fn solve_d16_p1(input: &str) -> usize {
         .split('\n')
         .flat_map(|line| line.split(','))
         .filter_map(|x| {
-            let value: usize = x.parse().unwrap();
+            let value: u16 = x.parse().unwrap();
             if rules.iter().any(|rule| rule.matches(value)) {
                 None
             } else {
@@ -112,18 +112,196 @@ fn solve_d16_p2(input: &str) -> usize {
         .product()
 }
 
-#[test]
-fn test_foo() {
-    const INPUT: &str = "class: 0-1 or 4-19
-row: 0-5 or 8-19
-seat: 0-13 or 16-19
-
-your ticket:
-11,12,13
-
-nearby tickets:
-3,9,18
-15,1,5
-5,14,9";
-    solve_d16_p2(INPUT);
+#[aoc(day16, part2, avx2)]
+fn solve_d16_p2_avx2(input: &str) -> usize {
+    unsafe { avx2::solve_d16_p2(input) }
+}
+
+#[cfg(all(target_arch = "x86_64", target_feature = "avx2"))]
+mod avx2 {
+    use super::{split_once, Rule};
+    use std::arch::x86_64::*;
+
+    struct RuleEval {
+        lo_start: [__m256i; 2],
+        lo_end: [__m256i; 2],
+        hi_start: [__m256i; 2],
+        hi_end: [__m256i; 2],
+    }
+
+    impl RuleEval {
+        #[target_feature(enable = "avx2")]
+        unsafe fn new(rules: &[Rule]) -> Option<Self> {
+            if rules.len() > 31 {
+                return None;
+            }
+            let lo_start = {
+                let mut lo_start = [_mm256_setzero_si256(); 2];
+                let lo_start_16 = &mut *(&mut lo_start as *mut [__m256i; 2] as *mut [i16; 32]);
+                let mut rules_iter = rules.iter();
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    lo_start_16[idx] = *rule.a.start() as i16 - 1;
+                }
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    lo_start_16[idx + 16] = *rule.a.start() as i16 - 1;
+                }
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    lo_start_16[idx + 8] = *rule.a.start() as i16 - 1;
+                }
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    lo_start_16[idx + 24] = *rule.a.start() as i16 - 1;
+                }
+                lo_start
+            };
+            let lo_end = {
+                let mut lo_end = [_mm256_setzero_si256(); 2];
+                let lo_end_16 = &mut *(&mut lo_end as *mut [__m256i; 2] as *mut [i16; 32]);
+                let mut rules_iter = rules.iter();
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    lo_end_16[idx] = *rule.a.end() as i16 + 1;
+                }
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    lo_end_16[idx + 16] = *rule.a.end() as i16 + 1;
+                }
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    lo_end_16[idx + 8] = *rule.a.end() as i16 + 1;
+                }
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    lo_end_16[idx + 24] = *rule.a.end() as i16 + 1;
+                }
+                lo_end
+            };
+            let hi_start = {
+                let mut hi_start = [_mm256_setzero_si256(); 2];
+                let hi_start_16 = &mut *(&mut hi_start as *mut [__m256i; 2] as *mut [i16; 32]);
+                let mut rules_iter = rules.iter();
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    hi_start_16[idx] = *rule.b.start() as i16 - 1;
+                }
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    hi_start_16[idx + 16] = *rule.b.start() as i16 - 1;
+                }
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    hi_start_16[idx + 8] = *rule.b.start() as i16 - 1;
+                }
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    hi_start_16[idx + 24] = *rule.b.start() as i16 - 1;
+                }
+                hi_start
+            };
+            let hi_end = {
+                let mut hi_end = [_mm256_setzero_si256(); 2];
+                let hi_end_16 = &mut *(&mut hi_end as *mut [__m256i; 2] as *mut [i16; 32]);
+                let mut rules_iter = rules.iter();
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    hi_end_16[idx] = *rule.b.end() as i16 + 1;
+                }
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    hi_end_16[idx + 16] = *rule.b.end() as i16 + 1;
+                }
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    hi_end_16[idx + 8] = *rule.b.end() as i16 + 1;
+                }
+                for (idx, rule) in rules_iter.by_ref().take(8).enumerate() {
+                    hi_end_16[idx + 24] = *rule.b.end() as i16 + 1;
+                }
+                hi_end
+            };
+            Some(RuleEval {
+                lo_start,
+                lo_end,
+                hi_start,
+                hi_end,
+            })
+        }
+
+        #[target_feature(enable = "avx2")]
+        unsafe fn eval(&self, value: u16) -> u32 {
+            let value = _mm256_set1_epi16(value as i16);
+            let within_lo = [
+                _mm256_and_si256(
+                    _mm256_cmpgt_epi16(self.lo_end[0], value),
+                    _mm256_cmpgt_epi16(value, self.lo_start[0]),
+                ),
+                _mm256_and_si256(
+                    _mm256_cmpgt_epi16(self.lo_end[1], value),
+                    _mm256_cmpgt_epi16(value, self.lo_start[1]),
+                ),
+            ];
+            let within_hi = [
+                _mm256_and_si256(
+                    _mm256_cmpgt_epi16(self.hi_end[0], value),
+                    _mm256_cmpgt_epi16(value, self.hi_start[0]),
+                ),
+                _mm256_and_si256(
+                    _mm256_cmpgt_epi16(self.hi_end[1], value),
+                    _mm256_cmpgt_epi16(value, self.hi_start[1]),
+                ),
+            ];
+            let valid = [
+                _mm256_or_si256(within_lo[0], within_hi[0]),
+                _mm256_or_si256(within_lo[1], within_hi[1]),
+            ];
+            let packed = _mm256_packs_epi16(valid[0], valid[1]);
+            _mm256_movemask_epi8(packed) as u32
+        }
+    }
+
+    #[target_feature(enable = "avx2")]
+    pub unsafe fn solve_d16_p2(input: &str) -> usize {
+        let (rules, rem) = split_once(input, "\n\nyour ticket:\n").unwrap();
+        let (my_ticket, nearby_tickets) = split_once(rem, "\n\nnearby tickets:\n").unwrap();
+
+        let rules: Vec<_> = rules.split('\n').map(|x| Rule::parse(x).unwrap()).collect();
+        assert!(rules.len() < 32);
+        let rule_eval = RuleEval::new(&rules).unwrap();
+        let mut candidates = [_mm256_set1_epi32((1i32 << rules.len()) - 1); 4];
+        let mut scratch_space = [_mm256_set1_epi32(1); 4];
+        for line in nearby_tickets.split('\n') {
+            let scratch_slice = &mut * (&mut scratch_space as *mut _ as *mut [u32; 32]);
+            for (field, scratch) in line.split(',').zip(scratch_slice.iter_mut()) {
+                let field = field.parse().unwrap();
+                *scratch = rule_eval.eval(field);
+            }
+
+            if scratch_space.iter().copied().any(|elem| {
+                _mm256_movemask_epi8(_mm256_cmpeq_epi32(elem, _mm256_set1_epi32(0))) != 0
+            }) {
+                continue;
+            }
+
+            for (candidate, valid_bitmask) in candidates.iter_mut().zip(scratch_space.iter()) {
+                *candidate = _mm256_and_si256(*candidate, *valid_bitmask);
+            }
+        }
+
+        let candidates = &mut * (&mut candidates as *mut _ as *mut [u32; 32]);
+        let candidates = &mut candidates[..rules.len()];
+        while candidates.iter().copied().any(|x| x.count_ones() > 1) {
+            for idx in 0..candidates.len() {
+                let candidate = candidates[idx];
+                if candidate.count_ones() == 1 {
+                    let mask = !candidate;
+                    for before in &mut candidates[..idx] {
+                        *before &= mask;
+                    }
+                    for after in &mut candidates[idx + 1..] {
+                        *after &= mask;
+                    }
+                }
+            }
+        }
+        my_ticket
+            .split(',')
+            .map(|x| x.parse::<usize>().unwrap())
+            .zip(candidates.into_iter().map(|x| x.trailing_zeros() as usize))
+            .filter_map(|(field, rule_idx)| {
+                if rules[rule_idx].name.starts_with("departure") {
+                    Some(field)
+                } else {
+                    None
+                }
+            })
+            .product()
+    }
 }