Nice little game!
Am I crazy, or are the amounts of health which die gives predetermened and tied to the animation? Also I felt that spikes damage was also constant for each spike, but again I might be wrong.
Music and art are really good.
Yes, the screen does shake when you take damage, but its magnitude does not depend on anything. For the spikes, there is actually a glitch where you take 9 HP instead of 4 because both the main player collider and ground check collider take 4 and 5 HP respectively, adding to a total of 9 HP of damage taken (can bring you from full health to half a heart). However, it is possible that only one of the colliders hit the spike, so you can take only 4 or 5 HP of damage. Thanks for the feedback!