v1.1: bubble-towers-1.p8.png
- add upgrade sprites to tower_upgrades.pdf
- add cost number in upgrade pop-up
- add tower description pop-up during upgrading
- change cursor color to orange
- fix numbers of fixed slow-down tower in tower_upgrades.pdf
- fix "blocked" fast enemies in double slow-down towers
- fix typo in manual: "shoot flying"
v1.0: bubble-towers-0.p8.png
- Initial feature-complete release