Love the retro art style and feel that's always a trusty lure for us NES kids. Upbeat music as well perfectly compliments the pace.
Given the importance of how jumping was to the game design, I wish the jumping mechanic was iterated on with more detail (particularly reflecting time length sensitivity of input to determine how high / low the player can jump, instead of a static-height high jump). Conversely, felt the "Interact" input was unnecessary and the buttons should've just triggered upon collision (and would've been more satisfying if the sprites were replaced by a "pressed down" graphic instead of freed from the scene).
Was impressed by the level design and felt it moved fairly smoothly (though there were some areas where I wondered if I took the right turns / went in the right directions).
The spikes have unforgiving hitboxes, especially blended with the visual effects to note "malfunction," and there was that one area where the series of down spikes, up spikes, and deathpits along with the lack of control the player has during the jump mechanic that I found nearly unpassable.
I think this was compounded by the fact that a sense of purpose wasn't really indicated for the player's journey. Who am I and why am I trying to advance through these levels? What's the purpose of collecting coins? If these questions were more explicitly answered, I think it would provide player motivation to persist through the limiting parts of the core mechanic and try to advance through daunting areas of the level design.
Found the increased malfunctions as part of the game's progression system to be an interesting choice—though personally prefer if the player is rather rewarded for surviving than punished.
Love the style, if not a little too Mario-imitative. Most of all, impressed by the programming fundamentals and art for a bug-free experience. Good job team!