```ts
export function crossUp(readings: number[], level: number): number {
    if (readings.length === 0) return 0;

    let crossingCount = 0;
    for (let i = 1; i < readings.length; i++) {
        if (readings[i] > level && readings[i - 1] <= level) {
            crossingCount++;
        }
    }

    return crossingCount;
}
```