Thank you for your feedback! It means a lot to us.
The idea is that the monsters are hiding in specific spots to mislead you even if you memorize the drawing. Currently, the only hint at monsters is with the glowing paint, but it was intentionally made unreliable due to the randomness of the light flickering, which added to the fear aspect. However, I'm not opposed to adding subtle cues to hint that there is a monster nearby to make the "trial and error" aspect of the game a lot less unforgiving and to make it a bit easier to detect monsters (without making it too obvious). I can understand the frustration of having to start all over after spending a lot of time on a drawing, especially in the later levels; fortunately, we have plans to add a "free draw" mode in a future update so players can paint as much as they want without needing to worry about monsters. There are also plans to add a difficulty system, which changes the quota and how many monsters are hiding at a time. We'd like to give players more flexibility with the game to ensure the best possible experience while still providing a fair challenge.