Unlocking


 * Completing Korma level 11 unlocks: Vic 20 and Endurance.


 * Completing Korma level 20 unlocks: Super New Ship Type 1, and Madras levels 1-30.


 * Completing Madras level 11 unlocks: C64, and Korma levels 21-30.


 * Completing Madras level 30 unlocks: Thrusty Mode, Super New Ship Type 2, and Vindaloo levels 1-40.


 * Completing Vindaloo level 11 unlocks levels 31-40 on Korma and Madras.


 * Completing Vindaloo level 40 unlocks Super New Ship Type 3, and all Phaal levels.


 * Completing Phaal level 11 unlocks levels 41-50 on all lower difficulties.


 * Completing Phaal level 50 unlocks Super New Ship Type 4.

The semi-official summary: To unlock things, play more.