Q: Index in sequence with reset [R/dplyr]

Just new to R and programming in general; I'm trying to count the number of rows observed with value > N within each group until values >= are observed, at which point, the count resets.

data <- tibble(id=1:10, 
  val=c(1,5,6,1,2,1,300,4,1,300), 
  group=c(1,1,1,3,2,1,1,1,1,3))

What my table looks like:
 id                                  val                             group
 1                                     1                                 1
 2                                     5                                 1
 3                                     6                                 1
 4                                     1                                 3
 5                                     2                                 2
 6                                     1                                 1
 7                                   300                                 1
 8                                     4                                 1
 9                                     1                                 1
10                                   300                                 3

For example, I want to count the number of rows until I see values > 100 and then reset the count:

 id                                  val                             group          count
 1                                     1                                 1              0
 2                                     5                                 1              1
 3                                     6                                 1              2
 4                                     1                                 3              0
 5                                     2                                 2              0
 6                                     1                                 1              3
 7                                   300                                 1              4
 8                                     4                                 1              0
 9                                     1                                 1              1
10                                   300                                 3              1

I've thought about adding an extra column and summing it up until the condition is observed, but I don't think that works the way I expect it to.

data_count <- mutate(data, c=1)
data_count <- grouped_by(data_count) %>% mutate(count=ifelse(val>100, cumsum(c), 0)

     id                                  val                             group          count
     1                                     1                                 1              1
     2                                     5                                 1              1
     3                                     6                                 1              1
     4                                     1                                 3              1
     5                                     2                                 2              1
     6                                     1                                 1              1
     7                                   300                                 1              1
     8                                     4                                 1              1
     9                                     1                                 1              1
    10                                   300                                 3              1

Thanks!