Total shit

level 2 seems totally impossible , must have tried it 60 times so far and cant complete

I have searched for a very similar game I played on amiga 500 for centuries without luck, and am very happy I found this game.

Issues:
- Enemies are flying circlewise or countercirclewise If they "lost" the wall they were following. Idea: If they do such a circle for 3 or 4 times, let them randomly go straight north / south / east / west, until they find a wall again they can "follow". This way, they wont look bugged any more.

Gameplay/Feeling:
- If gems/rocks drop "sidewards" because they are located on another gem/rock, and the player stands under them, it "feels wrong" that the player survives. Maybe it is necessary though for gameplay reasons.
- If the player runs from left to right in one row and a mob runs from right to left in a row below/above (or vice versa, also up/down), the player doesn´t die. This also "feels wrong", however, level 19 tells me that this is intended for gameplay reasons.
- The "sight range" of 3 blocks is - considering the fast movement of the mobs - too low. You can not plan longer routes this way, which is frustrating in an action game. Imagine playing Super Mario but only seeing 3 blocks far in front of Mario. When walking to the left side or up, the sight range is 4 blocks instead. This is not consistent. Idea: Why not let the player choose the block viewrange using the buttons WASD, this way, he could "spy" on areas himself (He still would have to be on screen, no full map knowledge - searching the "Exit" is an important part of the game.)?
- It is very difficult to exactly "time" when to change the movement direction. This way, you very often run too far, or not far enough, which is especially hazardous in case you are being followed by creeps - or run into them.
- I died several times collecting gems because I turned around too fast and ran into a gem that was still falling. This had a very frustrating feel.

Ideas:
- Once a level is completed, say "congratulations, you finished level XX". On the button, let it say "Play level XY" - This way we know where we are in the game.

Level difficulty:
For the game mechanics are easy to learn, I would recommend rearranging the levels. Here is my (approximated) death toll | time usage | frustration / boredom:
Level 1: 0 | 2 mins
Level 2: 250 | 3 days | very high frustration <- this should be the new level 25
Level 3: 30 | 4 h | high frustration (because being killed by rocks IS frustrating) <- should be a later level, ~ level 15
Level 4: 150 | 1 day | no frustration / boredom
Level 5: 2 | 30 mins | easy
Level 6: 40 | 2 h | medium
Level 7: 25 | 1 h | tricky! interesting level, hard difficulty
Level 8: 50 | 1h | medium boredom (having to manually hunt multiple yellow butterflys bores a bit)
Level 9: 125 | 4h | tricky!
Level 10: 25 similar to 8, but far less boring because many gems to collect inside.
Level 11: 25 | 30 mins | Another "time attack" type level! I kinda love these :)
Level 12: 40 | 1 h | Without the walls but more "strategically" placed butterflies, this was kind of tricky! should be before Lv 8 / Lv10, though
Level 13: 10 | 2h | Very interesting concept, timeattack that forces you to build own walls to have enough gems when trapping the "plague"
Level 14: 25 | 25 mins | rather easy
Level 15: 20 | 30 mins | very high boredom/frustration in a bad way. I´d recommend to make changes to this level. Reason: You pretty much figure out after 2 minutes what you have to do, then end up hating yourself a lot if something fails, because it just feels like wasted time.
Level 16: 3 | 5 mins | This actually should be level 2. very easy.
Level 17: 50 | 2h | This is an interesting level again!
Level 18: 10 | 30 mins | This should be ~ level 5. Learning manual killing yellow butterflies.
Level 19: 25 | 1h | Tough! Definetely not bored on this one
Level 20: 100 | 3h | This was really hard. Nice.
Level 21: 120 | 3h | Also really hard
Level 22: 20 | 1h | Medium difficulty. Bit frustrating to have to wait for the plague here.
Level 23: 5 (however, considering my experience from previous levels) | 40 mins | Hard, nice level
Level 24&25: 10 | 20 mins | Medium difficulty. Having to blast up the walls to continue was taught long ago, so these 2 level can be put on easier numbers.

Ok, here are my thoughts:
I love it. This is exactly what I have missed so long ever since I lost my Amiga 500.
Whatever new you add to your game, with the small changes above you already have a decent game, which I would put as bonus content under a "play the first version of this game"- button in the case that you decide to adapt major changes in the future. Integrate it as bonus content into your future games!
- I loved having small "changes" in levels when the game is newly loaded, for a change.
- As previously mentioned, Level 2 was VERY difficult, I would urgently recommend putting it as one of the very last levels.
- The character animation still needs a bit of work. For example, if you only "tap" the right arrow, it looks like the character moves while standing

For future patches:
- Even if the door is open, still show how many gems we collected ( for example: 250/100). We want to know. It might even be interesting to put them into a cookie and save them, so we can try to collect more if we ever decide to play the level again (that is the target: increasing the games replayability!)
- Add a map, where the 25 levels are on
- Add lives. 25 gems give an extra life. -> This should come simultaneously with a cookie, which stores the amount of lives / levels unlocked.
- The rocks look blurry, compared to the other textures.
- Add gore xD Nothing against squishing that yellow butterfly under a rock, after it exploded 25 times on us, right? :D (check out Spike: a love story here on newgrounds for gore mechanics, haha: https://www.newgrounds.com/portal/view/568517 )
- a level editor and a database where we can upload/download new maps

Oh, and one tiny note: I really dislike having games where I control the char with my right hand (keyboard) and then have to click with the mouse in menus (also right hand), especially if I die a lot (In this game, I have to). If the mouse is not relevant for your game, make the menus completely controllable via keyboard. Gives a more "round" feel.

EDIT: Ok, I see that you realigned the levels. But I do not think that you had to delete level 2, it just should have been put as the last one.

I guess it's ok, although not very fun. Plays like the kind of game you would find in an old 600 games shareware compilation