implement simulation shell

src/lib/sim/TickDriver.cpp

@@ -0,0 +1,21 @@
+#include "TickDriver.h"
+
+#include "Tick.h"
+
+int TickDriver::advance(double elapsedWallMs, double gameSpeedMultiplier)
+{
+    m_accumulatorMs += elapsedWallMs * gameSpeedMultiplier;
+
+    int ticks = 0;
+    while (m_accumulatorMs >= kTickDurationMs)
+    {
+        m_accumulatorMs -= kTickDurationMs;
+        ++ticks;
+    }
+    return ticks;
+}
+
+void TickDriver::reset()
+{
+    m_accumulatorMs = 0.0;
+}