The puzzles are well designed. However the timer is kinda ruining the experience imo.
I feel like if you are designing a puzzle game, you gotta let the player have time to think. Otherwise design a more action focused game where its more about quick reaction time rather than thinking. That's my opinion anyway.
On death, the game goes back to the menu and then starts a random level next time. Maybe allow to resume from the last level instead so a player can feasibly finish the game?