Change padding orientation in graphic

I would like to know if there is a possibility to change the color fill orientation of the following graphic

WhatIwantisforthecolorstobefilledfromtheoutsidetotheinside.Anyonehaveanyideas?

dat<-structure(list(Category=structure(1:15,.Label=c("ID1", "ID2", "ID3", "ID4", "ID5", "ID6", "ID7", "ID8", "ID9", "ID10", 
             "ID11", "ID12", "ID13", "ID14", "ID15"), class = "factor"),
    Percentage = c(0.8, 0.32, 0.15, 0.6, 0.4, 0.5, 0.3, 0.7, 1, 0.8, 0.3, 0.9, 0, 0.2, 0.46)),
  .Names = c("Category", "Percentage"), row.names = c(NA, 15L), class = "data.frame")

ggplot(data = dat) +
  geom_col(aes(x = Category, fill = Category, y = Percentage), width = 1) +
  geom_hline(yintercept = 1, color = "darkgrey", size = 1) + #ponto de partida
  geom_segment(aes(x = 1.5, xend = 4.5, y = .75, yend = .75), color = "darkgrey", size = 1) +#2017
  geom_segment(aes(x = 5.5, xend = 15.5, y = .75, yend = .75), color = "darkgrey", size = 1) +#2017
  geom_segment(aes(x = 1.5, xend = 15.5, y = .5, yend = .5), color = "darkgrey", size = 1) +#2018
  geom_segment(aes(x = .5, xend = 4.5, y = .25, yend = .25), color = "darkgrey", size = 1) +#2019
  geom_segment(aes(x = 5.5, xend = 15.5, y = .25, yend = .25), color = "darkgrey", size = 1) +#2019
  geom_vline(xintercept = seq(.5, 15.5, by = 1), color = "darkgrey", size = 1) +
  coord_polar() +
  theme_minimal() +
  labs(x = NULL, y = NULL) +
  theme(axis.text.y = element_blank(),
        legend.position = "none",
        panel.grid = element_blank())