In Obake, you have three weapons that can be fired at any time. Firing a weapon slows your ship down somewhat. Firing two makes you go slower, and three slows you down to a crawl. Normally, this would be an incentive to not fire all your weapons at once. However, you need to be precise in order to dodge some of the more complex bullet patterns the bosses throw at you.
However, firing also heats your ship. Get it hot enough, and your weapons cease to function until the temperature goes back to reasonable levels.
Your ship also starts going faster again, smacking you directly into whatever bullet you were trying to dodge.*
Now, there is a way to cool your ship if you don't have enough time or leg room to let go of the trigger. You can graze. That is, you get very, very close to bullets. This is what the title of this post refers to. The more weapons you have firing, the more damage you deal to the boss, and the slower you go. Yet, you need to constantly graze lest you overheat.
Now for the evil bit. There is a score multiplier that changes, depending on how hot your ship is. If the meter reads 53% for example, your multiplier is x1.53. Thus, the player is encouraged to keep their heat gauge high, putting themselves in even greater peril because of the promise of a bigger reward. Granted, most players don't care about score. I am certain that a good portion of Obake's audience will, however.
*JackMackerel suggests; "If you overheat, have a trollface flash really really quickly on the screen." I'm tempted to put this in.
Edit: Shlapintogan mentioned something interesting that I overlooked. Keeping your heat high increases your multiplier, but discourages you from grazing. We managed to come up with a workable solution for this mutual exclusivity, though. Grazing has its own separate multiplier, which isn't as lucrative as the heat multiplier.
To prevent the player from having to look away from the play field to check their multipliers, sound cues are used. For example, there is a tick sound played every time you graze a bullet. As your graze multiplier increases, the pitch of the tick changes. Likewise, the heat meter has its own sound and pitch changes.
Thus, the player has three options.
1) Play it safe, and don't worry about score. Graze only when you need to, and keep your heat low.
2) Graze when you can, and get a small bonus.
3) Keep your heat up, and get a large bonus.
4) Attempt to juggle both, possibly net record scores, get bitches, and lose a bit of sanity.
The last option would be impossible for all but a small set of players, so Shlap suggested this. Have a region (45 to 55% or so) that if you stay in for both bars, nets you a bonus. Once both bars are in the sweet spot, the player is notified via a chirping sound. As the player sustains the bonus, the chirping gets more rapid, culminating in a ding that tells the player they have completed the bonus. Look to Beat Hazard for refinement and inspiration.