The Oil Blue is a great game that could use a few improvements in a sequel (I would usually say update, but I realize that is impossible).

Graphics: The graphics are serviceable and fit the mood. The old timey look of the interface for the machines is nice. There is a ton of blue.

Music: The music is suitably disturbing on the opening screen with some nice, more relaxing sounds for the actual days. The unlockable music is great as well.

Gameplay: Pretty great set of tasks for the drilling. The groundwells are a very simple risk/reward drill with you having to decide how much attention you want to give it vs. how fast you want to pump oil. I usually erred on pumping somewhat slow with a level 10 at max upgrade.

The oil derrick seems to require the most attention, which is why it is considered the hardest. I honestly mostly ignore this for the two to follow.

The pumpjack is probably the easiest way to get a ton of barrels. It requires the least attention and has the best reminder system.

The drilling rig is fun - it is basically a touchscreen minigame. It requires a lot of attention when you actually find oil, as it builds stress quickly, even when fully upgraded (because of the increase in oil found). I found that it has the highest potential to give oil of any of the drills.

The repairing minigames are okay too, but a few are slightly bugged (the making-a-square-of-lights repair minigame occasionally doesn't visibly switch squares if pressed too early, but still works).

The game provides quite a challenge, as it is very difficult to keep up all of the drills going well at once as they should be. It is a little stressful with all of the horns and such, but once you realize that having a few machines in the red is less bad than making sure you sell barrels, it becomes less so.

Minor Quibbles: The way of selling oil barrels should be changed in a sequel to allow for the up arrow on the keyboard to be held or to provide a sell max oil button or something. It is not a big deal when you only have 20 barrels of oil in storage, but when you have 75 barrels of oil in storage and it is maxed out, it would be nice to be able to sell them all immediately or hit the up arrow.

I have a similar feeling about the upgrades - when you can only buy upgrades to one or two machines, it is not even a problem, but when you have 8 to upgrade to level 20, it takes a while to buy all upgrades (though by the time all of the manual upgrades unlock, you have tons of time to do this and repair everything, so it is less of a problem).

My only quibble with the drilling machines is the reminder bell for the groundwells - it occurs when there are ~5 charges left in a battery, so it is thoroughly not useful after the first few levels of upgrades. It should activate with around 20 to provide time to make changes. All other alerts are appropriate.

Lastly, when you upgrade a machine, it brings up an info block about the upgrade you have just bought, which is helpful when you get automatic upgrades but a little annoying when you manually buy upgrades and have 100 to click away (but again, you have tons of time before the day really starts to do this).

Overall: I would give The Oil Blue a 9/10. It is not a game for the easily stressed, but it is fun and each day is pretty quick. I hope for a sequel that improves on the minor quibbles and provides a larger number of drilling machines.