diff --git a/index.html b/index.html
index 579c177..f06ca34 100644
--- a/index.html
+++ b/index.html
@@ -81,6 +81,16 @@
                 <div class="input"></div>
             </div>
         </div>
+        <!-- TODO debug panel?
+        - current tic
+        - list of actors, or currently pointed-to actor?
+        <div class="debug">
+            <button>« 4 tics</button>
+            <button>« 1 tic</button>
+            <button>1 tic »</button>
+            <button>4 tics »</button>
+        </div>
+        -->
     </main>
     <main id="editor" hidden>
         <header>
diff --git a/js/format-c2m.js b/js/format-c2m.js
index 5311925..da4dd46 100644
--- a/js/format-c2m.js
+++ b/js/format-c2m.js
@@ -138,8 +138,8 @@ const TILE_ENCODING = {
     0x49: ['swivel_nw', 'swivel_floor'],
     0x4a: ['swivel_ne', 'swivel_floor'],
     0x4b: ['swivel_se', 'swivel_floor'],
-    // 0x4c: Time bonus : '#next'
-    // 0x4d: Stopwatch : '#next'
+    0x4c: ['stopwatch_bonus', '#next'],
+    0x4d: ['stopwatch_toggle', '#next'],
     // 0x4e: Transmogrifier : 
     // 0x4f: Railroad track (Modifier required, see section below) : 
     // 0x50: Steel wall : 
@@ -163,7 +163,7 @@ const TILE_ENCODING = {
     // 0x66: Mirror Melinda : '#direction', '#next'
     // 0x68: Bowling ball : '#next'
     // 0x69: Rover : '#direction', '#next'
-    // 0x6a: Time penalty : '#next'
+    0x6a: ['stopwatch_penalty', '#next'],
     0x6b: ['#mod8?', ['floor_custom_green', 'floor_custom_pink', 'floor_custom_yellow', 'floor_custom_blue']],
     0x6d: ['#thinwall/canopy', '#next'],
     // 0x6f: Railroad sign : '#next'
@@ -240,7 +240,7 @@ export function parse_level(buf) {
     let level = new util.StoredLevel;
     let full_view = new DataView(buf);
     let next_section_start = 0;
-    let extra_hints;
+    let extra_hints = [];
     let hint_tiles = [];
     while (next_section_start < buf.byteLength) {
         // Read section header and length
diff --git a/js/game.js b/js/game.js
index 95be78a..d9b7e34 100644
--- a/js/game.js
+++ b/js/game.js
@@ -178,13 +178,16 @@ export class Level {
         this.player = null;
         this.actors = [];
         this.chips_remaining = this.stored_level.chips_required;
+        this.bonus_points = 0;
+
+        // Time
         if (this.stored_level.time_limit === 0) {
             this.time_remaining = null;
         }
         else {
-            this.time_remaining = this.stored_level.time_limit;
+            this.time_remaining = this.stored_level.time_limit * 20;
         }
-        this.bonus_points = 0;
+        this.timer_paused = false;
         this.tic_counter = 0;
         // 0 to 7, indicating the first tic that teeth can move on.
         // 0 is equivalent to even step; 4 is equivalent to odd step.
@@ -551,10 +554,9 @@ export class Level {
 
         // Advance the clock
         let tic_counter = this.tic_counter;
-        let time_remaining = this.time_remaining;
-        this.tic_counter++;
-        if (this.time_remaining !== null && this.tic_counter % 20 === 0) {
-            // 20 tics means one second!  Tic that time down
+        this.tic_counter += 1;
+        if (this.time_remaining !== null && ! this.timer_paused) {
+            let time_remaining = this.time_remaining;
             this.pending_undo.push(() => {
                 this.tic_counter = tic_counter;
                 this.time_remaining = time_remaining;
@@ -834,6 +836,36 @@ export class Level {
         }
     }
 
+    adjust_bonus(add, mult = 1) {
+        let current = this.bonus_points;
+        this.pending_undo.push(() => this.bonus_points = current);
+        this.bonus_points = Math.ceil(this.bonus_points * mult) + add;
+    }
+
+    pause_timer() {
+        if (this.time_remaining === null)
+            return;
+
+        this.pending_undo.push(() => this.timer_paused = ! this.timer_paused);
+        this.timer_paused = ! this.timer_paused;
+    }
+
+    adjust_timer(dt) {
+        let current = this.time_remaining;
+        this.pending_undo.push(() => this.time_remaining = current);
+
+        // Untimed levels become timed levels with 0 seconds remaining
+        this.time_remaining = Math.max(0, (this.time_remaining ?? 0) + dt * 20);
+        if (this.time_remaining <= 0) {
+            if (this.timer_paused) {
+                this.time_remaining = 1;
+            }
+            else {
+                this.fail("Time's up!");
+            }
+        }
+    }
+
     fail(message) {
         this.pending_undo.push(() => {
             this.state = 'playing';
diff --git a/js/main.js b/js/main.js
index 52580d6..775a657 100644
--- a/js/main.js
+++ b/js/main.js
@@ -508,7 +508,7 @@ class Player extends PrimaryView {
             this.time_el.textContent = '---';
         }
         else {
-            this.time_el.textContent = this.level.time_remaining;
+            this.time_el.textContent = Math.ceil(this.level.time_remaining / 20);
         }
         this.bonus_el.textContent = this.level.bonus_points;
         this.message_el.textContent = this.level.hint_shown ?? "";
@@ -557,7 +557,7 @@ class Player extends PrimaryView {
             else {
                 this.bummer_el.textContent = "";
                 let base = (this.conductor.level_index + 1) * 500;
-                let time = (this.level.time_remaining || 0) * 10;
+                let time = Math.ceil((this.level.time_remaining ?? 0) / 20) * 10;
                 this.bummer_el.append(
                     mk('p', "go bit buster!"),
                     mk('dl.score-chart',
diff --git a/js/tileset.js b/js/tileset.js
index 442512b..968fa71 100644
--- a/js/tileset.js
+++ b/js/tileset.js
@@ -188,7 +188,7 @@ export const CC2_TILESET_LAYOUT = {
     swivel_se: [12, 11],
     swivel_floor: [13, 11],
     // TODO some kinda four-edges thing again
-    // TODO stopwatch with a - sign??
+    stopwatch_penalty: [15, 11],
     paramecium: {
         north: [[0, 12], [1, 12], [2, 12]],
         east: [[3, 12], [4, 12], [5, 12]],
@@ -205,8 +205,8 @@ export const CC2_TILESET_LAYOUT = {
     walker: [0, 13],
     // TODO walker animations span multiple tiles, rgh
     helmet: [0, 14],
-    // 14: stopwatch
-    // 15: stopwatch with +
+    stopwatch_toggle: [14, 14],
+    stopwatch_bonus: [15, 14],
 
     blob: [0, 15],
     // TODO blob animations also span multiple tiles
diff --git a/js/tiletypes.js b/js/tiletypes.js
index 1350651..13bc935 100644
--- a/js/tiletypes.js
+++ b/js/tiletypes.js
@@ -392,6 +392,9 @@ const TILE_TYPES = {
                     }
                 }
             }
+            if (other.type.is_player) {
+                level.adjust_bonus(0, 0.5);
+            }
         },
     },
     thief_keys: {
@@ -406,6 +409,9 @@ const TILE_TYPES = {
                     }
                 }
             }
+            if (other.type.is_player) {
+                level.adjust_bonus(0, 0.5);
+            }
         },
     },
     forbidden: {
@@ -595,6 +601,39 @@ const TILE_TYPES = {
             }
         },
     },
+    // Time alternation
+    stopwatch_bonus: {
+        draw_layer: LAYER_ITEM,
+        blocks_monsters: true,
+        blocks_blocks: true,
+        on_arrive(me, level, other) {
+            if (other.type.is_player) {
+                level.remove_tile(me);
+                level.adjust_timer(+10);
+            }
+        },
+    },
+    stopwatch_penalty: {
+        draw_layer: LAYER_ITEM,
+        blocks_monsters: true,
+        blocks_blocks: true,
+        on_arrive(me, level, other) {
+            if (other.type.is_player) {
+                level.remove_tile(me);
+                level.adjust_timer(-10);
+            }
+        },
+    },
+    stopwatch_toggle: {
+        draw_layer: LAYER_ITEM,
+        blocks_monsters: true,
+        blocks_blocks: true,
+        on_arrive(me, level, other) {
+            if (other.type.is_player) {
+                level.pause_timer();
+            }
+        },
+    },
 
     // Critters
     bug: {
@@ -683,6 +722,7 @@ const TILE_TYPES = {
     },
 
     // Keys
+    // Note that red and blue keys do NOT block monsters, but yellow and green DO
     key_red: {
         draw_layer: LAYER_ITEM,
         is_item: true,
@@ -697,11 +737,15 @@ const TILE_TYPES = {
         draw_layer: LAYER_ITEM,
         is_item: true,
         is_key: true,
+        blocks_monsters: true,
+        blocks_blocks: true,
     },
     key_green: {
         draw_layer: LAYER_ITEM,
         is_item: true,
         is_key: true,
+        blocks_monsters: true,
+        blocks_blocks: true,
     },
     // Tools
     // TODO note: ms allows blocks to pass over tools
@@ -794,15 +838,47 @@ const TILE_TYPES = {
     },
     score_10: {
         draw_layer: LAYER_ITEM,
+        blocks_monsters: true,
+        blocks_blocks: true,
+        on_arrive(me, level, other) {
+            if (other.type.is_player) {
+                level.adjust_bonus(10);
+            }
+            level.remove_tile(me);
+        },
     },
     score_100: {
         draw_layer: LAYER_ITEM,
+        blocks_monsters: true,
+        blocks_blocks: true,
+        on_arrive(me, level, other) {
+            if (other.type.is_player) {
+                level.adjust_bonus(100);
+            }
+            level.remove_tile(me);
+        },
     },
     score_1000: {
         draw_layer: LAYER_ITEM,
+        blocks_monsters: true,
+        blocks_blocks: true,
+        on_arrive(me, level, other) {
+            if (other.type.is_player) {
+                level.adjust_bonus(1000);
+            }
+            level.remove_tile(me);
+        },
     },
     score_2x: {
         draw_layer: LAYER_ITEM,
+        blocks_monsters: true,
+        blocks_blocks: true,
+        on_arrive(me, level, other) {
+            if (other.type.is_player) {
+                level.adjust_bonus(0, 2);
+            }
+            level.remove_tile(me);
+        },
     },
 
     hint: {