Would have been better to call it Sonic Isometric.
Yes, Flickies Island, the main goal is to collect the Flickies who have been trapped in machines to search for Chaos Emeralds by Doctor Robotnik. There are 7 stages in the game...
Green Grove Zone
Rusty Ruin Zone
Spring Stadium Zone
Diamond Dust Zone
Volcano Valley Zone
Gene Gadget Zone
Panic Puppet Zone
Throughout all those seven stages (except in the final act of Panic Puppet), you must collect flickies by breaking Robotnik's robots, this task becomes a bit dull after a while, you have do this for 13 acts as well.
The Chaos Emeralds are the second thing needed to be collected, if you don't collect them all, Robotnik can destroy the world anytime he wants with The Final Weapon. This ending however is silly because it's not really good enough, it says...
"As long as I have this super weapon, I can destroy the world any time I like, see you again, Sonic."
Really, it should have been more like the ending that appears when you get all the Chaos Emeralds or something. The Chaos Emeralds are only accessaible by paying Tails or Knuckles 50 rings and winning their bonus rounds.
The stages are detailed and look nice but the special stages are terrible, the backgrounds in them are really irritating but still.
Overall, the stages are nice and colorful, but the flicky collecting gets boring after a while, by the fifth stage you might wish it was the old Sonic ways, exploring the levels instead.