Riddles, brain puzzles and mathematical problems

[Romulator]

Your sister and your best friend have been acting rather suspiciously recently. One evening you notice your sister secretly pass a piece of paper into your friend's pocket. You wait for the right opportunity and remove the note to discover the following:

R1U0R0L4L6D5L7D1 L4U6R0R2U4 U6L0D8 R1D1R2.

R1U0L7L4D1U8R2R1 L2L3L8D4D5L2D3!

Confused, you record the secret message and return the piece of paper. The next day, while your sister is out, you look around the house and discover a scrap of paper in one of the waste paper bins. It has the following similar message written on it, but it seems to contain a clue:

R2D1R1L8 = TEST

Can you decode the original message and work out what your sister and best friend are up to?

I won't lie, first thought she was becoming a lesbian

Thinking about R, since there are two, we have R2 and R1. Comparing them in position relative to TEST, 2 places after R in the alphabet is T, and 1 after is S. Similar circumstances for the others, with one letter after D = E, and 8 letters after L = T - likely to put us off.

Using this:

Spoiler below!

Code: (Select All)

//Reference

ABCDEFGHIJKLMNOPQRSTUVWXYZ

//Message
R1 = S
U0 = U
R0 = R
L4 = P
L6 = R
D5 = I
L7 = S
D1 = E

L4 = P
U6 = A (Go back to A, as Z is 5 letters after U)
R0 = R
R2 = T
U4 = Y

U6 = A
L0 = L
D8 =  L

R1 = S
D1 = E
R2. = T.


R1 = S
U0 = U
L7 = S
L4 = P
D1 = E
U8 = C (Like U6, go back to A. Becomes C)
R2 = T
R1 = S

L2 = N
L3 = O
L8 = T
D4 = H
D5 = I
L2 = N
D3! = G!

Therefore, the secret message is:

SURPRISE PARTY ALL SET.
SUSPECTS NOTHING!