diff --git a/assets/Web437_IBM_BIOS.woff b/assets/Web437_IBM_BIOS.woff
new file mode 100644
index 0000000..9daecb3
Binary files /dev/null and b/assets/Web437_IBM_BIOS.woff differ
diff --git a/assets/Web437_IBM_VGA_8x16.woff b/assets/Web437_IBM_VGA_8x16.woff
new file mode 100644
index 0000000..1f1508d
Binary files /dev/null and b/assets/Web437_IBM_VGA_8x16.woff differ
diff --git a/index.html b/index.html
index 98bd407..60f3573 100644
--- a/index.html
+++ b/index.html
@@ -11,6 +11,8 @@
     canvas {image-rendering: pixelated; margin: auto;
             position:absolute; left:0; right:0; top:0; bottom:0}
     @font-face { font-family: 'text'; src:url(assets/font.ttf) }
+    @font-face { font-family: 'ibm-vga'; src:url(assets/Web437_IBM_VGA_8x16.woff) }
+    @font-face { font-family: 'ibm-bios'; src:url(assets/Web437_IBM_BIOS.woff) }
   </style>
 </head>
 <body>
diff --git a/src/constants.js b/src/constants.js
index b6d3672..5fe5015 100644
--- a/src/constants.js
+++ b/src/constants.js
@@ -121,7 +121,7 @@ export const PLAYER_STARTING_TOOLS = [
 
 export const PANEL_WIDTH = 400;
 export const PANEL_HEIGHT = 300;
-export const PANEL_FONT_SIZE = 10;
+export const PANEL_FONT_SIZE = 8;
 export const PANEL_TITLE_FONT_SIZE = 16;
 export const PANEL_BG_COLOR = '#666';
 export const PANEL_BORDER_COLOR = '#333';
diff --git a/src/gfx.js b/src/gfx.js
index 806a208..271d14d 100644
--- a/src/gfx.js
+++ b/src/gfx.js
@@ -163,8 +163,12 @@ export function drawParagraph(ctx, text, x, y, w, h, color) {
 }
 
 export function loop(fn) {
+  let lastTime = performance.now();
   (function looped() {
-    fn();
+    const now = performance.now();
+    const dt = Math.min((now - lastTime) / 1000, 0.1);
+    lastTime = now;
+    fn(dt);
     requestAnimationFrame(looped);
   })();
 }
diff --git a/src/main.js b/src/main.js
index 9aa1fc8..5132ff9 100644
--- a/src/main.js
+++ b/src/main.js
@@ -6,7 +6,7 @@ import {clamp, deg2rad, distance, parable, random, randomInt, vec, wrap} from '.
 import {PROJECTILE_TYPES} from './projectiles.js?v=5';
 import {generateSky} from './sky.js?v=5';
 import {playTickSound} from './sound.js?v=5';
-import {clipTerrain, closestLand, collapseTerrain, generateTerrain, isTerrain, landHeight} from './terrain.js?v=5';
+import {clipTerrain, closestLand, collapseTerrain, generateTerrain, isTerrain, landHeight, startCollapseTerrain, collapseTerrainStep} from './terrain.js?v=5';
 import {sample, shuffle} from './utils.js?v=5';
 import {EXPLOSION_TYPES} from './weapons.js?v=5';
 import {drawPanelBg, drawPanelTitle, drawPanelText, drawPanelDivider, drawPanelMenu, getPanelBounds} from './panel.js?v=5';
@@ -22,6 +22,8 @@ let particles = [];
 let screenShake = 0;
 let trajectories = [];
 let idle = false;
+let dt = 0;
+let collapseState = null;
 let winner;
 
 let score = 0;
@@ -162,6 +164,7 @@ function initAllPlayerStats() {
       deaths: 0,
       shotsFired: 0,
       wins: 0,
+      lastDamageSource: null,
     });
   }
 }
@@ -200,7 +203,7 @@ function updateMarket() {
       const item = marketItems[menuState.selected];
       const itemData = MARKET_ITEMS[item];
       const humanPlayer = players.find(p => !p.ai);
-      if (humanPlayer && score >= itemData.price && item !== 'babyMissile') {
+      if (humanPlayer && score >= itemData.price && item !== 'babyMissile' && WEAPON_TYPES[item]) {
         score -= itemData.price;
         let existingWeapon = humanPlayer.weapons.find(w => w.type === item);
         if (existingWeapon) {
@@ -285,6 +288,7 @@ function initPlayers() {
       player.kills = 0;
       player.deaths = 0;
       player.shotsFired = 0;
+      player.lastDamageSource = null;
     }
     players = existingPlayers;
   } else {
@@ -310,6 +314,7 @@ function initPlayers() {
         deaths: 0,
         shotsFired: 0,
         wins: 0,
+        lastDamageSource: null,
       });
     }
   }
@@ -435,7 +440,7 @@ function update() {
     for (let i=projectiles.length-1; i>=0; i--) {
       const projectile = projectiles[i];
       const projectileType = PROJECTILE_TYPES[projectile.type];
-      if (projectileType.update(projectile, terrain, projectiles, trajectories, explosions)) continue;
+      if (projectileType.update(projectile, terrain, projectiles, trajectories, explosions, dt)) continue;
       projectileType.stop(projectile);
       projectiles.splice(i, 1);
     }
@@ -463,6 +468,8 @@ function update() {
         let remainingDamage = damage;
         if (!damage) continue;
 
+        if (explosion.source) player.lastDamageSource = explosion.source;
+
         if (player.shield) {
           remainingDamage = clamp(0, damage-player.shield.energy, Infinity);
           player.shield.energy = clamp(0, player.shield.energy-damage, Infinity);
@@ -478,8 +485,11 @@ function update() {
   }
 
   else if (state === 'land-collapse') {
-    collapseTerrain(terrain);
-    state = 'land-players';
+    if (!collapseState) collapseState = startCollapseTerrain(terrain);
+    if (collapseTerrainStep(terrain, collapseState)) {
+      collapseState = null;
+      state = 'land-players';
+    }
   }
 
   else if (state === 'land-players') {
@@ -518,6 +528,9 @@ function update() {
     createParticles(x, y, PLAYER_EXPLOSION_PARTICLE_POWER, c);
     dyingPlayer.dead = true;
     dyingPlayer.deaths++;
+    if (dyingPlayer.lastDamageSource && dyingPlayer.lastDamageSource !== dyingPlayer) {
+      dyingPlayer.lastDamageSource.kills++;
+    }
     state = 'explosions';
   }
 
@@ -912,7 +925,8 @@ function drawStatus() {
   drawText(foreground, `Round: ${round}/${totalRounds}   Score: ${score}`, W-8, 18, 'white', 'right');
 }
 
-loop(() => {
+loop((deltaTime) => {
+  dt = deltaTime;
   update();
   draw();
 });
diff --git a/src/panel.js b/src/panel.js
index cbca199..4d0aef6 100644
--- a/src/panel.js
+++ b/src/panel.js
@@ -20,7 +20,7 @@ export function drawPanelBg(ctx) {
 export function drawPanelTitle(ctx, text) {
   const x = PANEL_X + PANEL_WIDTH / 2;
   const y = PANEL_Y + 20;
-  ctx.font = `${PANEL_TITLE_FONT_SIZE}px text`;
+  ctx.font = `${PANEL_TITLE_FONT_SIZE}px ibm-vga`;
   ctx.textBaseline = 'top';
   ctx.textAlign = 'center';
   ctx.fillStyle = 'black';
@@ -30,7 +30,7 @@ export function drawPanelTitle(ctx, text) {
 }
 
 export function drawPanelText(ctx, text, x, y, color = 'white', align = 'left') {
-  ctx.font = `${PANEL_FONT_SIZE}px text`;
+  ctx.font = `${PANEL_FONT_SIZE}px ibm-bios`;
   ctx.textBaseline = 'top';
   ctx.textAlign = align;
   ctx.fillStyle = 'black';
diff --git a/src/projectiles.js b/src/projectiles.js
index 85bea0f..5ee9a15 100644
--- a/src/projectiles.js
+++ b/src/projectiles.js
@@ -23,13 +23,14 @@ export const PROJECTILE_TYPES = {
     stop(projectile) {
       projectile.osc.stop(0);
     },
-    update(projectile, terrain, projectiles, trajectories, explosions) {
+    update(projectile, terrain, projectiles, trajectories, explosions, dt) {
       const prevProjectile = {...projectile};
       const {weapon, player, wind} = projectile;
       const weaponType = WEAPON_TYPES[weapon.type];
       let exploded = false;
+      const iterations = Math.max(1, Math.round(PROJECTILE_ITERATIONS_PER_FRAME * dt * 60));
 
-      for (let i=0; i<PROJECTILE_ITERATIONS_PER_FRAME; i++) {
+      for (let i=0; i<iterations; i++) {
         const {ox, oy, a, p, t} = projectile;
 
         const [x, y] = parable(
@@ -69,7 +70,7 @@ export const PROJECTILE_TYPES = {
         ) {
           const explosionSpec = weaponType.explosion;
           const explosionType = EXPLOSION_TYPES[explosionSpec.type];
-          explosions.push(explosionType.create(explosionSpec, x, y));
+          explosions.push({...explosionType.create(explosionSpec, x, y), source: player});
           // @ts-ignore: canvas color hack
           createParticles(x, y, p, terrain.color);
           exploded = true;
@@ -108,7 +109,7 @@ export const PROJECTILE_TYPES = {
     stop(projectile) {
       projectile.osc.stop(0);
     },
-    update(projectile, terrain, projectiles, trajectories, explosions) {
+    update(projectile, terrain, projectiles, trajectories, explosions, dt) {
       const prevProjectile = {...projectile};
       const {state, weapon, player, wind} = projectile;
       const weaponType = WEAPON_TYPES[weapon.type];
@@ -116,7 +117,8 @@ export const PROJECTILE_TYPES = {
 
       if (state === 'flying') {
         const {ox, oy, a, p, t} = projectile;
-        for (let i=0; i<PROJECTILE_ITERATIONS_PER_FRAME; i++) {
+        const iterations = Math.max(1, Math.round(PROJECTILE_ITERATIONS_PER_FRAME * dt * 60));
+        for (let i=0; i<iterations; i++) {
           let [x, y] = parable(
             t, ox, oy, deg2rad(180+a),
             p / PROJECTILE_POWER_REDUCTION_FACTOR,
@@ -183,12 +185,13 @@ export const PROJECTILE_TYPES = {
 
       else if (state === 'rolling') {
         const {x, y, d} = projectile;
-        const nextY = landHeight(terrain, x+d);
+        const rollSpeed = Math.max(1, Math.round(dt * 60));
+        const nextY = landHeight(terrain, x + d * rollSpeed);
 
         if (nextY < y || y > H || isTank(x, y)) {
           projectile.state = 'explode';
         } else {
-          projectile.x += d;
+          projectile.x += d * rollSpeed;
           projectile.y = nextY;
         }
       }
@@ -197,7 +200,7 @@ export const PROJECTILE_TYPES = {
         const {x, y, p} = projectile;
         const explosionSpec = weaponType.explosion;
         const explosionType = EXPLOSION_TYPES[explosionSpec.type];
-        explosions.push(explosionType.create(explosionSpec, x, y));
+        explosions.push({...explosionType.create(explosionSpec, x, y), source: player});
         // @ts-ignore: canvas color hack
         createParticles(x, y, p, terrain.color);
         finished = true;
@@ -255,7 +258,7 @@ export const PROJECTILE_TYPES = {
       }];
     },
     stop() {},
-    update(projectile, terrain, projectiles, trajectories, explosions) {
+    update(projectile, terrain, projectiles, trajectories, explosions, dt) {
       const {player, weapon, ox, oy, a, p, wind, n, s} = projectile;
       const projectileType = PROJECTILE_TYPES.normal;
 
@@ -268,7 +271,7 @@ export const PROJECTILE_TYPES = {
       }
 
       const alive = projectileType.update(
-        projectile.payload, terrain, projectiles, trajectories, explosions
+        projectile.payload, terrain, projectiles, trajectories, explosions, dt
       );
 
       if (!alive) {
diff --git a/src/terrain.js b/src/terrain.js
index d036816..c1de650 100644
--- a/src/terrain.js
+++ b/src/terrain.js
@@ -72,6 +72,43 @@ export function collapseTerrain(ctx, ) {
   cacheImageData(ctx);
 }
 
+export function startCollapseTerrain(terrain) {
+  return {};
+}
+
+export function collapseTerrainStep(terrain, state) {
+  const {width, height} = terrain.canvas;
+  const imageData = terrain.getImageData(0, 0, width, height);
+  const data = imageData.data;
+  let anyMoved = false;
+
+  for (let y = height - 2; y >= 0; y--) {
+    for (let x = 0; x < width; x++) {
+      const idx = (y * width + x) * 4;
+      const belowIdx = ((y + 1) * width + x) * 4;
+      if (data[idx + 3] > 0 && data[belowIdx + 3] === 0) {
+        data[belowIdx] = data[idx];
+        data[belowIdx + 1] = data[idx + 1];
+        data[belowIdx + 2] = data[idx + 2];
+        data[belowIdx + 3] = data[idx + 3];
+        data[idx] = 0;
+        data[idx + 1] = 0;
+        data[idx + 2] = 0;
+        data[idx + 3] = 0;
+        anyMoved = true;
+      }
+    }
+  }
+
+  if (!anyMoved) {
+    cacheImageData(terrain);
+    return true;
+  }
+
+  terrain.putImageData(imageData, 0, 0);
+  return false;
+}
+
 export function isTerrain(ctx, x, y) {
   const index = coords2index(ctx.canvas.width, x, y) * 4;
   return cachedImageData.data[index+3] > 0;