Not an easy way... but not too difficult
For example, a way to do that...
You could use a user variable like "speedBoost" with an initial value of "0".
Then, make a duplicate of your Physics_4_1_0.asm script (the script that is assigned to your "Physics" element in the "Project Settings > Script Settings") for example "Physics_withSpeedBoost.asm" and assign that script to your "Physics" element.
Now, modify the Physics_withSpeedBoost.asm, around line 41, just
before the:
Add :
Code:
CPX player1_object
BNE +
LDA tempMaxSpeed
CLC
ADC speedBoost
STA tempMaxSpeed
+
Finally to increase the speed, just make a powerUp script (to assign to one of your pickup object) that will modify that boost variable:
Code:
;; increase the speed by 16:
LDA speedBoost
CLC
ADC #$10 ;; #16
STA speedBoost