Acid Missile is a level pack made by FuriousFox, mostly consisting of maps submitted to the OLDC during the Final Demo era. It contains three single player zones – Waterfall Valley, Storm Ruins, and Gloom Metropolis – as well as a custom final boss. The gameplay is the same as standard SRB2, with three acts per zone, one of them being a boss act. It is well-known for being one of the first Single Player level packs for SRB2, as well as one of the few completed ones.
There are currently three single player zones, consisting of three acts per zone. Additionally, there is a fourth boss level which serves as the last level in the main campaign. Acid Missile has the same gameplay concept as vanilla SRB2, with the first two acts of a zone being levels with a goal sign, three emblems, and two emerald tokens to collect; the boss levels utilize the Egg Mobile and Egg Slimer, as well as two modified bosses not seen in standard SRB2 playthrough. For the Version 2.0 port, three custom special stages were added, which each consist of a square design of three tiers. A certain number of rings must be collected to move on to the next tier where more rings may be collected. A bonus "Emerald Practice" level which serves as the hub stage for the unlockable of the same name, and two hidden (but not unlockable) maps that haven't been fully ported from Version 1.09.4 add to a total number of sixteen levels.
Acid Missile has two unlockables.