diff --git a/functions/src/Grid.ts b/functions/src/Grid.ts
index eb88a56..e70a1ec 100644
--- a/functions/src/Grid.ts
+++ b/functions/src/Grid.ts
@@ -31,7 +31,7 @@ class Grid<T> {
     return this.data[this.index(x, y)];
   }
 
-  setAt(x: number, y: number, value: T) {
+  setAt(x: number, y: number, value: T): void {
 
     if (!this.isInBounds(x, y)) {
       throw Error(`Invalid coordinate: (${x}, ${y})`);
@@ -53,7 +53,7 @@ class Grid<T> {
     return x >= 0 && x < this.maxX && y >= 0 && y < this.maxY;
   }
 
-  inBoundsNeighbors(x: number, y: number, includeDiagonal: boolean = false): Vector2[] {
+  inBoundsNeighbors(x: number, y: number, includeDiagonal = false): Vector2[] {
 
     const res = [
       new Vector2(x + 1, y),
@@ -75,7 +75,7 @@ class Grid<T> {
   /**
    * Pastes the given grid into this grid, with it's top left position at the given coordinate
    */
-  paste(grid: Grid<T>, posX: number, posY: number) {
+  paste(grid: Grid<T>, posX: number, posY: number): void {
 
     if (posX + grid.maxX > this.maxX || posY + grid.maxY > this.maxY) throw Error(`Can't paste grid at (${posX}, ${posY}), this grid is not big enough`);
 
diff --git a/functions/src/day14.ts b/functions/src/day14.ts
index ec375b2..d80ae8f 100644
--- a/functions/src/day14.ts
+++ b/functions/src/day14.ts
@@ -76,7 +76,7 @@ class Day14 implements Day {
 
     const { orig, mapping } = Day14.parseInput(input);
 
-    let counts: CharCounts = {};
+    const counts: CharCounts = {};
     const cache = new Map<string, CharCounts>();
     for (let i = 0; i < orig.length - 1; i++) {
 
@@ -120,7 +120,7 @@ class Day14 implements Day {
 
   }
 
-  mergeIntoLeft(left: CharCounts, right: CharCounts) {
+  mergeIntoLeft(left: CharCounts, right: CharCounts): void {
 
     for (const rightKey in right) {
       if (rightKey in left) {
@@ -131,7 +131,7 @@ class Day14 implements Day {
     }
   }
 
-  addOne(char: string, counts: CharCounts) {
+  addOne(char: string, counts: CharCounts): void {
 
     if (char in counts) {
       counts[char]++;
diff --git a/functions/src/day15.ts b/functions/src/day15.ts
index 261ccc6..4f8bd10 100644
--- a/functions/src/day15.ts
+++ b/functions/src/day15.ts
@@ -42,7 +42,10 @@ class Day15 implements Day {
       // Simulate a priority queue on distance:
       searchStack.sort((a, b) => distances.at(b.x, b.y) - distances.at(a.x, a.y));
 
-      const cur = searchStack.pop()!;
+      const cur = searchStack.pop();
+
+      if (!cur) throw Error("???");
+
       if (cur.x === destination.x && cur.y === destination.y) {
         break;
       }
diff --git a/functions/src/day16.ts b/functions/src/day16.ts
index 47f9065..c0e47c9 100644
--- a/functions/src/day16.ts
+++ b/functions/src/day16.ts
@@ -92,7 +92,7 @@ class Packet {
     return input.split("").map(s => parseInt(s, 16).toString(2).padStart(4, "0")).join("");
   }
 
-  static parseBinaryInput(binaryInput: string, start: number = 0): Packet {
+  static parseBinaryInput(binaryInput: string, start = 0): Packet {
 
     const version = parseInt(binaryInput.substr(start, Packet.VERSION_LENGTH), 2);
     const type = parseInt(binaryInput.substr(start + Packet.VERSION_LENGTH, Packet.TYPE_LENGTH), 2);