For the first some runs you could give a tip where is the "safe zone" on the bar, after some runs should be fine.
On higher levels you can make the "platforms" shake and fall to lava after some time, so it adds a bit of "action"
Fireballs shooting from walls or from lava are fine too, however id prefer make it aka "lava geyser", since fireballs may be not so easy to notice on mobile.
Obviously adding some "perks" will be nice too, collectible after every platforms each 1 use, ie. "Safe Cloud" (get back on platform when u die), "Lava Boots" (ability to run on lava for "x" seconds/platforms), "Lava Coat" (protects from 1 lava geyser), etc. etc.
Aint sure if i got any more ideas, have fun with your game