This is a fun concept, blending strategic thinking and real-time action, and very well built for the time given.
If you wanted to build it out you might consider some smoothing in the players favour to avoid long period of just having to shoot everything while you wait for the right number to come along, the simplest solution being to weight the number generation and use that to make ones that fit the node a bit more common than ones that don't. From there you can hone in on the difficulty/tedium sweet spot by altering the weighting as the range of acceptable numbers narrows.