using window function lag() to calculate percentage change

Question

I'm trying to calculate the difference between each row that each shares a specific attribute. For example, I have a week's worth of playtime of three games (RDR2, GTA5, Spyro) and I have calculated what percent of each day is spent on each game and I want to see what the percent change is day over day.

Hence, I wrote:

percent - LAG(percent, 1) OVER (PARTITION BY game ORDER BY time DESC) AS games_delta

but instead of getting the desired output of:

 |-------------------------------|
 | TIME    GAME   PERCENT  DELTA |
 |-------------------------------|
 | Dec 10  RDR2   25       15    |
 | Dec 10  GTA5   50       40    |
 | Dec 10  Spyro  25      -55    |
 | Dec 9   RDR2   10      -22    |
 | Dec 9   GTA5   10       10    |
 | Dec 9   Spyro  80       13    |
 | Dec 8   RDR2   33       ...
 | Dec 8   GTA5   0        ...
 | Dec 8   Spyro  67       ...

I get multiplicities of the games and totally wrong game-delta!:

 |-------------------------------|
 | TIME    GAME   PERCENT  DELTA |
 | Dec 10  RDR2   25       2     |
 | Dec 10  RDR2   25       4     |
 | Dec 10  RDR2   25      -4     |
 | Dec 10  RDR2   25       4     |
 | Dec 10  GTA5   10       5  ...

Any suggestions? Thanks in advance!

Edit:

SELECT  time,
        game,
        percent,
        games_delta

I also have the following in my GROUP BY and ORDER BY:

GROUP BY time, game, percent, games_delta
ORDER BY time DESC

Edit 2:

Here's my CTE:

cte_table4 (time, games_delta) AS
(
    SELECT time,
            percent - LAG(percent, 1) OVER (PARTITION BY game ORDER BY time DESC) AS games_delta

    FROM cte_table3
)

Answer 1

Adding the aggregation GROUP BY in the same CTE as the LAG() will fix the issue