Spike damage behavior

In Sonic the Hedgehog for the Sega Megadrive, spikes were originally intended to be as lethal to Sonic as falling down a pit or being crushed to death. When Sonic is injured by anything, including a set of spikes, he will begin to flash, indicating he is invulnerable. However, if he lands on spikes, he will be harmed, regardless of whether he is flashing or not.

It is often mistakenly thought that this was caused by Sonic not becoming invulnerable at the appropriate time due to not landing on the ground (thus dieing in the long row of spikes), however, even if he is flashing on the ground, he can jump or fall into a set of spikes and still be harmed or die while flashing. This is cause of debate as to whether it was indeed a 'bug' or an intended feature.

Removal

• An official ROM hack was released as part of Sonic Mega Collection, called "JP2", where the spike 'bug' was removed.
• drx actually created his own ROM hack before the release of Sonic Mega Collection, with the spike 'bug' removed. He later released the source code, or rather instructions for removing the 'bug' in an ASM file (disassembly). drx's bugfix has been implemented in Hivebrain's Sonic 1 Plus and South Island Adventure ROM hacks.
• FraGag made a tutorial on how to remove the spike 'bug', it is avaliable here.