Congratulations! You finished a game.
I gave up on the spider... the bullets just don't reach it.
Almost everything the player does in this game is poorly executed. The character is slow, the jump is small, all this happens as if with a delay.
Never draw grass on platforms if you have a 1 bit style game. ALL your grass looks like spikes and the player thinks he shouldn't step on it.
After the player has somehow learned how to cope with platforming, you give him a new mechanic - shooting and immediately make this shooting unbearable: slow bullets, limited ammunition, bullets disappear if you collide with an enemy bullet, you must manage to kill the enemy in 20 seconds. .. dude...