/*Default color theme: bright*/
:root {
    --header-color: #2FEED4;
    --background-color: #e0ffff;
    --dropbtn-color: #47AFE6;
    --dropbtn-hover-color: #9DDBFA;
    --sidebar-content-color: #66D2FF;
    --calc-btn-hover-color: #94E3E3;
    --text-color: #000000;
    --close-btn-color: #C41700;
    --close-btn-active-color: #731500;
    --transition-speed: 0.6s;
}

/*Color theme: dark*/
.dark-theme {
    --header-color: #000000;
    --background-color: #1A1A1A;
    --dropbtn-color: #8C009C; 
    --dropbtn-hover-color: #BA47C9;
    --sidebar-content-color: #720782;
    --calc-btn-hover-color: #080808;
    --text-color: #B8B8B8;
}

/*Adjust overall element*/
* {
    font-family: system-ui;
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    transition: background-color var(--transition-speed), color var(--transition-speed), border var(--transition-speed);
}
        
/*Adjust related element/class/id on itself*/
header {
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: relative;
}

header::before {
    content: '';
    position: absolute;
    background-color: var(--header-color);
    top: 0px;
    bottom: 0px;
    left: 0px;
    right: 0px;
    z-index: -1;
    filter: blur(1.5px);
}

/*Wrap drop-down menu together in one place*/
.header-left {
    display: flex;
    gap: 20px;
}

/*Adjust logo*/
#logo {
    width: 40px;
    height: 40px;
}

h1 {
    color: var(--text-color);
    letter-spacing: 5px;
}

body {
    background-color: var(--background-color);
    color: var(--text-color);
}

/*Drop-down menu*/
.dropdown-container {
    position: relative;
    display: inline-block;
}
        
.dropdown {
    background-color: var(--dropbtn-color);
    color: var(--text-color);
    border: 2px solid var(--text-color);
    padding: 0.7rem 1.5rem;
    border-radius: 10px;
    font-size: 1rem;
    font-weight: 550;
    display: flex;
    cursor: pointer;
    align-items: center;
}
        
.dropdown:hover {
    background-color: var(--dropbtn-hover-color);
    transform: translateY(4px);
}

.dropdown:active {
    background-color: var(--dropbtn-color);
    transform: translateY(10px);
}
        
.content {
    background-color: var(--dropbtn-hover-color);
    color: var(--text-color);
    display: none;
    overflow: hidden;
    position: absolute;
    width: 200px;
    border-radius: 10px;
    margin-top: 5px;
}  
        
.content button {
    color: var(--text-color);
    font-size: 1rem;
    background: none;
    border: none;
    padding: 12px 16px;
    text-decoration: none;
    display: block;
    width: 100%;
    text-align: left;
    cursor: pointer;
}
        
.content button:hover {
    background-color: var(--dropbtn-color);
    color: var(--text-color);
    font-size: larger;
    font-weight: 800;
    transition: bottom 0.5s ease;
}
        
.show {
    display: block;
    animation: fadeIn 0.3s ease;
}
        
/*Sidebar*/
.sidebar {
    background-color: var(--sidebar-content-color);
    color: var(--text-color);
    position: absolute;
    top: 0;
    left: -500px;
    width: 450px;
    height: auto;
    padding: 2rem;
    z-index: 5;
    transition: left 0.8s ease;
}

.sidebar.active {
    left: 0;
}

.sidebar-header {
    color: var(--text-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid;
}
        
.close-btn {
    color: var(--text-color);
    background: none;
    border: none;
    font-size: 30px;
    font-weight: 600;
    cursor: pointer;
    transition: color 0.1s;
}
        
.close-btn:hover {  
    color: var(--close-btn-color);
}

.close-btn:active {
    color: var(--close-btn-active-color);
}

/*Overall main area*/
main {
    display: flex;
    flex: 1;
    max-width: 1800px;
    margin: 1rem auto;
    padding: 0 2rem;
    gap: 2rem;
    align-items: flex-start;
    justify-content: flex-end;
}

/*Calculator*/
.calculator {
    border-radius: 15px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.05);
    padding: 2rem;
    margin-top: 1rem;
    width: 600px;
    height: 750px;
    
    position: relative;
    z-index: 2;
    order: 1;
}

.calculator::before {
    content: '';
    position: absolute;
    background-color: var(--header-color);
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    border-radius: 20px;
    z-index: -1;
    filter: blur(2px);
}

.calc-display {
    background-color: var(--background-color);
    opacity: 0.7;
    border: 1px solid var(--dropbtn-color);
    border-radius: 10px;
    padding: 1rem;
    margin-bottom: 1.5rem;
    text-align: right;
    font-size: 2.5rem;
    font-weight: 500;
    min-height: 100px;
    display: flex;
    align-items: center;
    justify-content: flex-end;
    cursor: text;
    overflow-x: auto;
}
        
.calc-btns {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
}
        
.calc-btn, .calc-btn-opera, .calc-btn-equal, .calc-btn-clear {
    background-color: var(--background-color);
    color: var(--text-color);
    padding: 2rem;
    font-size: 1.8rem;
    border: none;
    border-radius: 15px;
    cursor: pointer;
    transition: all 0.3s ease;
}

.calc-btn-opera, .calc-btn-equal {
    color: var(--dropbtn-color);
    font-weight: 500;
}

.calc-btn:hover, .calc-btn-opera:hover, .calc-btn-equal:hover {
    background-color: var(--calc-btn-hover-color);
    transform: translateY(4px);
}

.calc-btn:active, .calc-btn-opera:active, .calc-btn-equal:active {
    background-color: var(--dropbtn-color);
    transform: translateY(10px);
}

.calc-btn-clear {
    color: red;
    font-weight: 600;
}

.calc-btn-clear:hover {
    background-color: var(--close-btn-color);
    transform: translateY(4px);
}

.calc-btn-clear:active {
    background-color: var(--close-btn-active-color);
    transform: translateY(10px);
}

/*Advance function*/
.advancedFunction {
    width: 300px;
    margin-top: 1rem;
    position: relative;
    left: auto;
    right: auto;
    margin-left: 1.5rem;
    
}

.advanced-toggle {
   background-color: var(--header-color);
    color: var(--text-color);
    border: 1px solid var(--dropbtn-color);
    padding: 1rem 1.5rem;
    border-radius: 10px;
    font-size: 1.2rem;
    font-weight: 550;
    cursor: pointer;
    width: 100%;
    text-align: center;
    transition: all 0.3s ease;
    margin-bottom: 0.5rem;
    z-index: 2;
}

.advanced-toggle:hover {
    background-color: var(--dropbtn-hover-color);
    transform: translateY(4px);
}

.advanced-toggle:active {
    transform: translateY(10px);
}

.advanced-content {
    border-radius: 12px;
    padding: 0.8rem;
    display: none;
    animation: fadeIn 0.3s ease;
    position: relative;
    background-color: var(--sidebar-content-color);
    z-index: 0;
}

.advanced-content::before {
    content:'';
    position: absolute;
    background-color: var(--sidebar-content-color);
    top: 4rem;
    bottom: 0;
    left: 0;
    right: 0;
    border-radius: 20px;
    z-index: -1;
    display: none;
}

.advanced-content.active {
    display: block;
}

.advanced-calc-btns {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
}

.adv-btn {
    background-color: var(--background-color);
    color: var(--text-color);
    border: none;
    padding: 1.5rem;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1.15rem;
    transition: all 0.2s ease;
}

.adv-btn:hover {
    background-color: var(--calc-btn-hover-color);
    transform: translateY(4px);
}

.adv-btn:active {
    background-color: var(--dropbtn-color);
    transform: translateY(10px);
}

/*Calculation history*/
#historyList {
    max-height: 400px;
    overflow-y: auto;
    margin-bottom: 1rem;
}

.history-item {
    background: rgba(255, 255, 255, 0.3);
    border-radius: 8px;
    padding: 12px;
    margin-bottom: 10px;
    border-left: 4px solid var(--dropbtn-color);
    display: flex;
    flex-direction: column;
    gap: 5px;
}

.history-expression {
    font-weight: bold;
    font-size: 1.2rem;
    word-break: break-all;
}

.history-result {
    color: var(--text-color);
    font-size: 1rem;
}

.history-controls {
    display: flex;
    gap: 10px;
    justify-content: center;
}

.history-btn {
    background: var(--dropbtn-color);
    color: var(--text-color);
    border: none;
    padding: 8px 16px;
    border-radius: 6px;
    cursor: pointer;
    transition: background-color 0.2s;
}

.history-btn:hover {
    background: var(--dropbtn-hover-color);
}

.history-use-btn, .history-delete-btn {
    background: var(--dropbtn-color);
    color: var(--text-color);
    border: none;
    padding: 4px 8px;
    border-radius: 4px;
    cursor: pointer;
    font-size: 0.8rem;
    margin-right: 5px;
    align-self: flex-start;
}

.history-use-btn:hover {
    background: var(--btn-color);
}

.history-delete-btn:hover {
    background: var(--close-btn-color);
}

/*Scroll bar for calculation history*/
#historyList::-webkit-scrollbar {
    width: 6px;
}

#historyList::-webkit-scrollbar-track {
    border-radius: 3px;
}

#historyList::-webkit-scrollbar-thumb {
    background: var(--dropbtn-color);
    border-radius: 3px;
}

#historyList::-webkit-scrollbar-thumb:hover {
    background: var(--dropbtn-hover-color);
}

#tutorial-content {
    max-height: 400px;     
    overflow-y: auto;
    padding-right: 8px;    
}

/*fraction display*/
.calc-display-wrapper{
        position: relative;
}

.fraction-editor{
        position: absolute;
        top: 50%;
        left: 0;
        transform: translate(0, -50%); 
        display: none;
        align-items: center;
        gap: 12px;
        background: lightblue;
        border-radius: 12px;
        padding: 10px;
        z-index: 2;
    }

/* when active, we show it */
.fraction-editor.active {
    display: flex;
}

/* stacked numerator / denominator */
.fraction-box {
    display: inline-flex;
    flex-direction: column;
    align-items: center;
}

/* these are REAL inputs but styled like plain text */
.fraction-input {
    width: 60px;
    text-align: center;
    font-size: 1.1rem;
    border: none;                 /* no box */
    outline: none;
    background: transparent;      /* match display */
    color: inherit;               /* same text color as display */
}

.fraction-bar{
        width: 100%;
        border-top: 1px solid black;
        margin: 3px 0;
}


.fraction-editor-buttons{
        display: flex;
        flex-direction: column;
        gap: 6px;
}

.small-btn {
       border: none;
       border-radius: 12px;
       padding: 4px 8px;
       font-size: 0.8rem;
       cursor: pointer;

}

/*Unit conversion*/
.unit-conversion-sidebar {
    background: var(--sidebar-content-color);
    position: fixed;
    top: 0;
    left: -600px;
    width: 500px;
    height: 100%;
    box-shadow: 5px 0 15px rgba(0,0,0,0.2);
    transition: left 0.3s;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    z-index: 1001;
}

.unit-conversion-sidebar.active {
    left: 0;
}

.unit-conversion-header {
    color: var(--text-color);
    border-bottom: 1px solid var(--text-color);
    padding: 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.unit-conversion-content {
    background: var(--sidebar-content-color);
    color: var(--text-color);
    flex: 1;
    padding: 20px;
    overflow-y: auto;
}

.conversion-input-group {
    background: var(--background-color);
    border: 1px solid var(--dropbtn-color);
    display: flex;
    flex-direction: column;
    gap: 15px;
    margin-bottom: 25px;
    padding: 20px;
    border-radius: 10px;
    opacity: 0.7;
}

.conversion-from, .conversion-to {
    gap: 12px;
    display: flex;
    align-items: center;
}

.conversion-input {
    background: var(--background-color);
    color: var(--text-color);
    border: 2px solid var(--dropbtn-color);
    padding: 12px;
    font-size: 18px;
    border-radius: 5px;
    text-align: right;
    flex: 1;
}

.conversion-input:focus, .conversion-select:focus {
    border-color: var(--dropbtn-hover-color);
    outline: none;
}

.conversion-select {
    background: var(--background-color);
    color: var(--text-color);
    border: 2px solid var(--dropbtn-color);
    padding: 12px;
    font-size: 16px;
    border-radius: 5px;
    cursor: pointer;
    flex: 1;
}

.conversion-arrow {
    color: var(--text-color);
    font-size: 1.8rem;
    font-weight: bold;
    display: flex;
    justify-content: center;
    align-items: center;
}

.conversion-result {
    background: var(--background-color);
    color: var(--text-color);
    border: 2px solid var(--dropbtn-color);
    flex: 1;
    padding: 12px;
    font-size: 18px;
    font-weight: bold;
    border-radius: 5px;
    text-align: right;
    min-height: 48px;
    display: flex;
    align-items: center;
    justify-content: flex-end;
}

.conversion-categories {
    gap: 10px;
    margin-bottom: 20px;
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
}

.category-btn {
    padding: 10px 20px;
    background: var(--background-color);
    color: var(--text-color);
    border: 2px solid var(--dropbtn-color);
    border-radius: 5px;
    cursor: pointer;
    font-size: 14px;
    transition: all 0.3s ease;
    min-width: 80px;
}

.category-btn:hover {
    background: var(--calc-btn-hover-color);
    transform: translateY(4px);
}

.category-btn:active {
    background: var(--dropbtn-color);
    transform: translateY(10px);
}

.unit-options {
    grid-template-columns: repeat(1, 1fr);
    display: grid;
    gap: 12px;
    margin-bottom: 15px;
}

.unit-option {
    background: var(--background-color);
    color: var(--text-color);
    border: 2px solid var(--dropbtn-color);
    font-size: 1rem;
    padding: 12px;
    border-radius: 8px;
    cursor: pointer;
    text-align: center;
    transition: all 0.3s ease;
}

.unit-option:hover {
    background: var(--calc-btn-hover-color);
    transform: translateY(4px);
}

.unit-option.selected {
    background: var(--dropbtn-color);
    color: var(--text-color);
    border-color: var(--dropbtn-color);
    transform: translateY(4px);
}

.unit-option:active {
    background: var(--dropbtn-hover-color);
    transform: translateY(10px);
}

.result-format {
    background: var(--background-color);
    border: 1px solid var(--dropbtn-color);
    font-size: 18px;
    font-weight: bold;
    text-align: center;
    margin: 20px 0 10px 0;
    padding: 15px;
    border-radius: 10px;
    opacity: 0.7;
}

.result-format span {
    color: var(--dropbtn-color);
    font-weight: 600;
}

.unit-conversion-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.5);
    display: none;
    z-index: 1000;
}

.unit-conversion-overlay.active {
    display: block;
}