Adding a booster and lava

You'll need a couple of additional colours to indicate a booster zone, where the hero can jump higher than normal, and a lava zone which will kill the hero and end the game.  I've chosen blue for the booster and red for lava.

Paint a booster zone and lava zone on your stage background - like this:

Now add some extra blocks to handle the booster and lava zones

The booster zone should only boost speed if the hero jumps onto it, not if he just moves sideways.  So we'll check to see if the downward speed (yspeed) is less than minus 3 (meaning he's falling onto it quite fast) before we give the speed boost.

For the lava, we don't need to check speed.  We just need to die gracefully.  There's no escape from lava!

The stop all control block just ends all processing and halts the game.

To improve the game, you can make a more elegant death sequence, together with an option to restart the game.