Index: binaries/data/mods/public/gui/summary/summary.js
===================================================================
--- binaries/data/mods/public/gui/summary/summary.js
+++ binaries/data/mods/public/gui/summary/summary.js
@@ -370,6 +370,54 @@
 		}
 
 	chart.series = series;
+
+	let size = chart.getComputedSize();
+	let pixel2index = g_GameData.sim.timeElapsed/1000
+			/g_GameData.sim.playerStates[1].sequences.time[1]
+			/(size.right-size.left);
+
+	// Add and update a tooltip to the Chart, showing the y-values for each player.
+	chart.onMouseMove = function(mouse){
+
+		// Calculate the index colsest to the time the mouse use is hoverieng over.
+		let index = ( pixel2index*(mouse.x - size.left) ).toFixed(0);
+
+		// Create [player-color, value] pairs
+		let values = [];
+
+		for (let series in chart.series)
+		{
+			if (index < chart.series[series].length)
+			{
+				values.push([setStringTags("■ ", { "color": chart.series_color[series] }),
+					chart.series[series][index].y]
+				);
+			}
+		}
+
+		values.sort(function (x,y){return y[1]-x[1]});
+
+		// Format the numbers
+		switch (chart.format_y)
+		{
+		case "PERCENTAGE":
+			values = values.map(value => value[0] + value[1] + "%");
+			break;
+
+		case "DECIMAL2":
+			values = values.map(value => value[0] + (Infinity === value[1] ?
+				"  " + g_InfinitySymbol : value[1].toFixed(2)
+			));
+			break;
+
+		default:
+			// Integers and default:
+			values = values.map(value => value[0] + value[1]);
+		}
+
+		chart.tooltip = timeToString(1000*g_GameData.sim.playerStates[1].sequences.time[index])
+			+ ":\n" + values.join("\n");
+	};
 }
 
 function adjustTabDividers(tabSize)