BLUE BOY (ブルーボーイ) I would buy this if it were available on Steam.
Not what I would call a rage game.
It's a fun and kind of creepy puzzle platformer.
I only have a handful of complaints to disclose:
(1) The out of place death sound.
When every other sound in the game are 8-Bit bips and blips so it's kind of jarring and immersion breaking to hear a random low-quality (but still realistic) grunt every time you die.
(2) The controls.
Whether intentional or not, the controls in this game seem to seize up at moments and overall seem very tank like and slow. Blue Boy has an acceptable jump height that can be adjust via how hard or lightly the Up arrow is pressed. While the implementation of such a feature was noble, it doesn't translate very well to keyboard controls in my opinion. Because of this, I often found myself jumping way too high and bumping a droplet when I never intended to. This frustration was amplified tenfold when the fire was introduced. Far too often I would die from the game deciding I wanted full jump height when I tapped the Up Arrow instead of a small hop.
(3) Deceptive level design. Probably the worst level in this game is Level 11 for the simple reason of deception. Without a shadow of doubt the most deaths I suffered happened there simply because of the deception of distance. The distance from one upper platform to a lower one is so close you would be forgiven for thinking you could control your fall and save yourself by landing there... but nope.
The hitboxes on either Blue Boy or the platforms or maybe both at the same time are so big combined with the fact that Blue Boy drops like a stone very easily and cruelly tricks the player into, as I said before, thinking they could maybe save their self by landing on a platform below.
So say, on Level 11 as I was speaking of, I hop over to the coin on the left and grab it. What do I do next? Well, I fall to the wall-mounted platform just before the landing where the coin sits. Then what? Any other 2D platformer would dictate that I could run from the wallside platform and use the momentum to land on the lower platform and continue on my merry way but not here. Here I have to first jump back up to the next upper platform over from where the wallside platform is. Now can I make that momentum fall and reach the platform? Still no, I have to do a short bunny hop to land it, otherwise the game will completely ignore my trying to move onto the platform below as I fall and I end up falling right into the fire instead of landing on the platform.
Challenging design is one thing, but the hitboxes and gravity being seemingly deliberately set like that just seems cruel. It takes the more of the challenge of having the skill to beat the levels away and in it's place has the challenge of getting used to the flawed physics of the game.
I would say other than that this game is pretty solid. One more thing for the road, I started trying to collect all the coins but gave up about half way through when the mechanics of the game and level design left me with no explanation as to how getting some of the coins was even possible. If I may make a suggestion, I would only have the droplets be spawned by movement.
If not by default then implementation as a difficulty option would work as well.
Update 10/28/2020:
Not sure why I never mentioned this, but I actually did go back not long after initially posting this review and managed to collect every last coin. My reward? Some of the most ridiculously difficult levels ever conceived. I get those bonus levels are there as challenges, but when the challenge is just "instant death fires everywhere" it's not very fun or inventive. I don't remember what my total death count was. Something in the three digit range, I guarantee.
LAB 
Zelda: Lampshade 
Wolfenstein 5K Flash 
Generic FPS 
Madness interactive 
Portal: The Flash Version 
Damnation: DooM Game e1m1