The ending was very sudden. But I get making games is hard :)
But despite that, here are my thoughts on the game:
Movement:
I commend you for implementing both a coyote jump as well as adding a jump buffer. The variable jump height also feels great. But the movement in general felt a bit flimsy. I think the jump is too high in relation to the speed of the character.
Art:
I like the style. The little characters were charming and the atmosphere in the village was very well done. I also like how you transition from the different areas with mixing tiles from the different biomes.
The miners I didn't immediately recognize as such. Maybe you could have given them little pickaxes or something.
When it comes to color, there are sadly some issues with the darker areas in the game. The cave and starting place for example have a tileset with almost the exact same color as the background. It makes it very hard to see and made me think that there would be lantern powerup or something along those lines and that's why I only entered the cave in my second playthrough. If it wasn't for the coins you put there this part would have been very frustrating.
Level Design:
The whole game is very much a giant horizontal line and the majority of the gameplay is to hold down the left or right arrow key. I would say this is boring level design but there is at least one thing it is good at and that's conveying a sense of scale. When you are in the mines the village really feels far away and it makes sense that the miners would like to know how it is there. But still it doesn't really make for a enjoyable map gameplay wise.
The dessert temple is the best when it comes to platforming but I'm sad that the floating backwards L didn't do anything. Was this also cut because of time issues ?
Thanks for making this I enjoyed my time.