I found a bug.
In level "line of sight" used 1 grate (leaving me with 2 money and 1 grate) and I still got gold medal.
Platinum medals are most like just a game desingers gifts for those who compleate levels better than programmer did. But as said in other reviews it may be frustrating to try get a platinum medal on level where it's not possible. So either but some marker on level to tell you can get one or even better make it possible in every level.
Also you could add super speed to run (or make current speed little higher). This might be just my PC but even on faster speed it took a long time to compleate some levels where there was lot of traveling.
And last thing. Put skip option to cut scenes. I loved them but when I saw that wyvern thing like 15 time (that was a hard gold) it became frustrating.