1. Some of the levels are tricky. I tweeted that level 19 was impossible. Actually, it was just fine.
2. The yellow squares are fixed and no mirrors can be placed on them.
3. The white dots on the grid: the beam must pass through it.
4. The black dots are on some of the mirrors and those mirrors must be used.
The menu indicates there are 49 levels. But there are 47 and I solved them all.
Laser Glow is fast and fun.
https://www.youtube.com/watch?v=t2PoPh2B9qo Funny video
Other Laser Puzzles (Not a complete list!)
Laser Maze 2015
Shoot & Reflect 3x3
RouteOut - not a laser game, but uses mirrors
Mirrors & Reflections
Guide the Light