Migoyugo

From BoardGameGeek:

Migoyugo is a two-player abstract strategy game played on an 8x8 board. No dice, no cards, no luck - just you and your opponent. The rules take about a minute to learn, but every time you think you've got it figured out, there's a deeper level of strategy to uncover. Players take turns placing Migos (temporary pieces) on any open square. When you place a piece that completes a line of exactly four of your color (horizontal, vertical, or diagonal), that piece becomes a Yugo, a permanent piece that can never be removed, but every Migo in that line disappears. Get four of your Yugos in an unbroken row and you win instantly. If neither player achieves this and the board fills up (or no legal moves remain), the player with the most Yugos wins. Equal Yugos means a draw. Every piece you place could be setting up your next Yugo, blocking your opponent, or holding your whole position together - but forming a Yugo might remove the very piece that was keeping you safe. Do you push for the instant win and risk leaving yourself exposed, or play it steady and grind out a win on Yugo count? Every move is a balancing act between attack and defense, and the best moves do both at once. One moment you're in complete control, but it only takes one misplaced piece and your opponent won't hesitate to deliver the fatal blow. -description from the designer