The gameplay is similar to the first game, but augmented (diluted?) by the addition of new features like the mine carts or hang gliders. The latter are notoriously difficult to control, but repeated taps on 'left' with occasional dives into updrafts should see you over the spikes. Sonic also gets his first loops to run through, although they are far less serene than their 16-bit counterparts, with jerky animation and much less control.
Above: The enemies were less of a threat in the sequel, unlike the terrain
The game is harder too on Game Gear, mainly due to the smaller screen. But compensation comes in the form of an abundance of extra lives. Any decent player would see the life counter hit 9 by about the third level and then never dip below it again. A bit of a poor balance really – much death with hardly any consequence.
The emeralds return, but they are harder to find. One reviewer at the time even said they weren't in the game at all... but he couldn't have been looking very hard. Getting them all unlocks an extra (and good-looking) level, and the 'good' ending.
While the game was highly praised at the time, it hasn't aged as well as the original and suffers from being bigger without necessarily being better. Also, the graphical style is less subtle, which takes away a lot of the magic. As a result, it's arguably the weakest of all the original 2D Sonic games.