bug fixes

• a bug with 1-3 collectible letters disappearing has been fixed
  
• spike wall now works properly and kills players even during i-frames
  

gameplay changes

• thunder dash now has an 8-frame jump buffer when exiting a tunnel
  
• thunder dash now sets the dash timer to 23 frames of dash time after entering a tunnel only if the player's dash timer is under 23 frames.
  
• spike wall in 1-4 is now slower