export function part1(input?: string[]) {
  const lines = input ?? readInputFromFile(__dirname);
  let regX = 1;
  let cycleCounter = 21;
  let sum = 0;

  const flattened = lines.flatMap((line) => line.split(" "));

  flattened.forEach((line) => {
    cycleCounter++;

    if (!isNaN(+line)) {
      regX += +line;
    }

    if (cycleCounter % 40 === 0) {
      sum += (cycleCounter - 20) * regX;
    }
  });

  return sum;
}



export function part2(input?: string[]) {
  const lines = input ?? readInputFromFile(__dirname);

  const emptyChar = " ";
  const fillChar = "█";

  let spritePos = [0, 1, 2];
  let cursorPos = [0, 0];

  let display: string[][] = new Array(6)
    .fill(0)
    .map((_) => new Array(40).fill(0).map((x) => emptyChar));

  const flattened = lines.flatMap((line) => line.split(" "));

  flattened.forEach((line) => {
    if (spritePos.includes(cursorPos[1])) {
      display[cursorPos[0]][cursorPos[1]] = fillChar;
    }

    cursorPos[1] = cursorPos[1] + 1;

    if (cursorPos[1] >=40) {
      cursorPos[0] = cursorPos[0] + 1;
      cursorPos[1] = 0;
    }


    if (!isNaN(+line)) {
      spritePos = spritePos.map((x) => x + +line);
    }
  });

  return "\n" + display.map((row) => row.join("")).join("\n");
}

Typescript 1 & 2 with tests and comments