Placement of ships and placement constraints

[Atrixsanna]

Implementing placement of ships by entering the cursor position and then horizontal or vertical (or using the directional keys again).

• Ships cannot be placed next to eachother, nor overlap
• Ships may not be placed facing out-of-bounds
• placement should be previewed (possibly using a blinking cursor on multiple nodes; preview does not have to be as restrictive as the actual placement)