When adjusting alpha on a pixel from the color picker it's quite easy to "whiff" the alpha bar and replace your current color with black because the SV box's area for some reason extends several pixels below the alpha bar's. Demonstration in the below image:

I'd recommend the alpha

Via playtesting, the compass arrows (#29) were ignored, likely because they are right at the edge and outside the player's attention. If they are moved slightly inwards, they may become more noticeable.

Games that have these arrows also tend to draw them closer to the player rather than near the edge; e.g.

• GTA 1 & 2
• Fire Fight
• Crazy Taxi