I played the demo a couple times in the last few days. Got every dragon and data pad in every level. I think it's a very promising game and I look forward to the full release.
I love the aesthetic and premise. You've managed to take a very simple mechanic and make it fun in a very immediate way. The music fits the look well, and the whole thing just screams Y2K in a good way.
Honestly, the difficulty seemed fine - good, even. I died a few times getting used to the controls, but once I'd played for a few levels it became natural to move around and I didn't mind redoing levels. People coddled by modern games might get their hackles up a bit, but the design reminds me very strongly of old games that just had a simple gameplay loop and expected players not to be discouraged by a single death.
The only things I think need redesigning are some of the way gameplay elements are introduced. The centipedes have a few different parameters (short, long, back-and-forth, loop) and having them all shoved together in big spaces just feels kind of messy. Same with the collapsing floor panels: I didn't realize that I had to run across the orange ones because the starting area where I first saw them had several circuitous paths, so by the time I wanted to go across the orange panels I was already running just to save time. Then later I tried walking across them, died, and though "huh?"
Having multiple mechanics introduced together isn't BAD GAME DESIGN™ (I've played Flash games and Source mods for literal decades, and it's fun to have different things thrown at you) but there were definitely a few times in the centipede level where I wasn't properly able to judge how the electric panels worked and died because of it. I think I went through my first run of that level without realizing that some panels were always on.
On a technical level, there are a few things that need to be fixed either for your next demo or the final release:
- Every type of platform/object/block needs to have a way to become transparent, and the transparency effect should be less distracting. One level had some metal loops that were technically not obstructing my view, but the "bubble" effect to see through them made me lose track of my character for a fraction of a second. Some objects just don't turn transparent, like the lightning towers in either the fourth or fifth level which obstructed my view while I was walking below them.
- In the level with the collapsing platforms, the second half has a section where everything is on metal grating with two tiers. The way the camera is angled, a ramp in the "background" looks like it lines up perfectly with the foreground, so I walked to my death the first time I came to that section.
(This is actually a really fiendish optical illusion that I think you should use in more advanced levels! Forced perspective is such an underused mechanic!)
- The collision to pick up a dragon needs to be larger. There were a couple times when I walked almost on top of one but didn't pick him up, which could easily waste several minutes of progress.
- Dying before the first checkpoint in a level shouldn't count as an additional attempt, since you roll back to the exact same point as a fresh start.
Overall, I can tell this will be a solid little game once it's been polished. Keep at it!